[its.git] / system / nmtape.27

;;; Copyright (c) 1999 Massachusetts Institute of Technology
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License as
;;; published by the Free Software Foundation; either version 2 of the
;;; License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program; if not, write to the Free Software
;;; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

;********************************
;**
;** TO BE DONE:
;**
;** RECORDS LONGER THAN 1K
;** AUTOMATIC DETERMINATION OF DENSITY AND RECORD LENGTH WHEN READING
;** ALLOW CLOSE WHEN TAPE HAS BEEN TAKEN OFF
;** BE MORE FORGIVING OF CONTROLLER LOSSAGE
;** PASS .MTAPE TO JOB DEVICE
;** HAVE AN IGNORE ERRORS SWITCH
;** THIS HORRIBLE BLETCHEROUS IOT CODE SHOULD BE REDESIGNED
;**
;********************************


IFE TM10A+TM10B+TM03S,.ERR NO MAGTAPE CONTROLLER TYPE SELECTED
IFN TM10A,INFORM IO BUSS MAG TAPE,1
IFN TM10B,INFORM DATA CHANNEL MAG TAPE,1
IFN TM03S,INFORM RH11/TM03 MAG TAPE,1

IFN TM10P,[
$INSRT TM10
]
IFN TM03S,[
$INSRT TM03S
]
$INSRT JTWMAC

MSCBL==8                        ;Command buffer length
MGQDLL==10.                     ;PI level PDL length
IF2 IFN MNUMB-140600, .ERR IMPLICIT DEPENDENCY ON MNUMB
MSEOFP==210100                  ;High bit of MNUMB in MEMBLT is EOF flag
MSCHN==140500                   ;Other 5 bits of MNUMB is drive number

MTXP==410300,,                  ;BP to set/get transport number from IOCHNM
MUNITF==170300                  ;BP to set/get unit field in MTC CONI

IFN TM10P,[
;Tape controller commands
MNOPIN==10000                   ;NOP and interrupt when idle
MWRITE==4000                    ;Write data
MW3IN==14000                    ;Write data and long EOR gap
MSPRR==7000                     ;Space in reverse direction
MREAD==2000                     ;Read data
MSPFR==6000                     ;Space in forward direction
MSPFF==16000                    ;Space forward to EOF
MSPRF==17000                    ;Space reverse to EOF
MREWND==1000                    ;Rewind
MRWNDD==11000                   ;Rewind and unload
MWEOF==5000                     ;Write EOF mark
]

MGNRTY==10.                     ;Number of retries on read

;Modes in OPEN call
;
%MMOUT==1,,0                    ;Open for output, 0=>input
%MMBLK==2,,0                    ;Block mode, 0=>unit mode
%MMIMG==4,,0                    ;Image mode, 0=>Ascii
%MMCNK==10,,0                   ;"Chunk" mode, 0=>stream mode
%MMNSE==20,,0                   ;No skip to EOF on close, 0=>do skip
%MMEP==40,,0                    ;Even parity, 0=>odd
%MMDEN==300,,0                  ;Density select
                                ; 00=> "Default" - 1600 for KS/TU77
                                ; 01=> 800 BPI
                                ; 10=> 1600 BPI
                                ; 11=> 6250 BPI
%MM32B==400,,0                  ;"IBM" mode, write 8-bit bytes from LH 32 bits
                                ; 0=> core dump
%MMRSZ==7000,,0                 ;Record Size
                                ; Ranging binarily from 0=>1024. to 7=>8. bytes

\f
EBLK

SUBTTL MAG TAPE STORAGE AREA

MGVTC:  0                       ;Scratch word for virgin tape check
MGJDTI: 0                       ;"Wait for job done" time out value
MGNWRD: 0                       ;Number of words read in a PI level read
MGTBZY: -1                      ;Flag to get interrupt started
MGSFTI: 0                       ;Software interrupt in progress
MGUNIT: -1                      ;Unit expecting interrupt
MGWCW:  0                       ;"Wait for control word written" flag
LMIOWD: 0                       ;Last MIOWD

MSRAC:  BLOCK NMTCS             ;Transport software status flags
 %MA==1,,525252
 %MAEOF==400000                 ;4.9 EOF seen on read - must be 4.9
 %MAETR==200000                 ;4.8 EOT on internal read
 %MAETW==100000                 ;4.7 EOT on write
 %MAERR==040000                 ;4.6 PI level got an error
 %MARCE==020000                 ;4.5 Read compare error
 %MACTH==014000                 ;4.4 Core allocator says stop
                                ;4.3 "  (WHY 2 BITS?)
 %MASTP==002000                 ;4.2 Stop read ahead
 %MANWT==001000                 ;4.1 Nothing written on tape yet
 %MAEFA==000400                 ;3.9 EOF seen on read-ahead, user hasn't seen
 %MAESO==000200                 ;3.8 EOF read since open
 %MAMSO==000100                 ;3.7 Tape moved since first open
 %MAREW==000040                 ;3.6 "Tape is rewinding" flag
 %MARAC==000020                 ;3.5 Read active flag
 %MAMOL==000010                 ;3.4 Transport on line
 %MAWSW==000004                 ;3.3 Wants software (timing) interrupts
MGERRC: BLOCK NMTCS             ;Error count
MTCEFW: BLOCK NMTCS             ;Number of EOF's written at close
MGEOFR: BLOCK NMTCS             ;Number of EOF's since last read
MTPSAV: BLOCK NMTCS             ;Storage to restore P on EOF
MSCMDC: REPEAT NMTCS,0          ;Number of commands in command list
MGSPCD: BLOCK NMTCS             ;Spacing operation command
MGSCNT: BLOCK NMTCS             ;Spacing operation count
MGEOTT: BLOCK NMTCS             ;Timeout for detecting virgin tape
MSBUFP: REPEAT NMTCS,0          ;Mag tape MP<->PI buffer queue  in,,out
MSNBOL: BLOCK NMTCS             ;Number of buffers on list
MSCRW:  BLOCK NMTCS             ;R/W flag, -1=>output 0=>input
MSMPRC: BLOCK NMTCS             ;Words left in buffer
MSMPRP: BLOCK NMTCS             ;Next word in buffer
MTMDN:  REPEAT NMTCS,-1         ;Block active at MP
MGCABN: REPEAT NMTCS,-1         ;Buffer active at PI level
MTUSE:  REPEAT NMTCS,-1         ;Number of channels open on this transport
MTUSR:  REPEAT NMTCS,-1         ;User index of transport user
MTBLKS: BLOCK NMTCS             ;If write, buffer size
                                ;If read, size of last record read
MTMFNC: BLOCK NMTCS             ;.MTAPE function storage
MTMCNT: BLOCK NMTCS             ;.MTAPE count
MTMTAP: BLOCK NMTCS             ;MTAPE call word

MGCMTS: BLOCK NMTCS             ;PI level status info (CONI MTS or similar)
MGCMTC: BLOCK NMTCS             ;PI level controller info (CONI MTC or similar)

 IFN TM10P,[
MTCONO: REPEAT NMTCS,\.RPCNT_17+20 ;Prototype CONO word for each transport
 ]
 IFN TM03S,[
MTSELW: BLOCK NMTCS             ;Select word (TC reg val) for each transport
 MTSELM==3777                   ;density/format/parity/unit bits mask
MTWTFC: BLOCK NMTCS             ;-10 word count to tape frame conversion factor
 ]

;Build table of QDL (PI level stack) pointers
MGQDLP: REPEAT NMTCS,-MGQDLL,,CONC MGQD,\.RPCNT,-1

;Built storage for command lists and PI level stacks
REPEAT NMTCS,[
        CONC MSCB,\.RPCNT,:
                BLOCK MSCBL     ;Space for command list
                MGRCV           ;Fake "command", causes list to wrap around

                MGNCMD          ;Function on botton of Q PDL, gets new command
        CONC MGQD,\.RPCNT,:
                BLOCK MGQDLL    ;Space for PI level stack

        IFE .RPCNT,MSLCTB==.-MSCB0      ;Length of each table
]

;Build table of pointers for adding commands to command list
MTCMBP: REPEAT NMTCS,-MSCBL-1,,CONC MSCB,\.RPCNT,-1

;Build table of bytepointers for removing commands from command list
MGCMBP: REPEAT NMTCS,4400,,CONC MSCB,\.RPCNT,-1

;It is depressing to discover that the DUMP program sucks these directly
; out of the running ITS. If you change what's in here fix DUMP too.

MGEMTC: 0                       ;CONI MTC, at last error
MGEMTS: 0                       ;CONI MTS, at last error

IFE TM10B,[
MIOWD: BLOCK 2                  ;Channel program
]
IFN TM10A,[
MGDBRK: 0
        CONO MTS,1
        JRST 12,@MGDBRK
];TM10A

BBLK

\f
;Random Macros

;Enqueue and Dequeue buffers from the lists used to pass buffers between
; main program and PI level. Assumes W has a valid transport number...

DEFINE MTENQB REG,TEMP=TT
        SKIPG MSNBOL(W)         ;;Any buffers on list already?
        IFSKP.
         HLRZ TEMP,MSBUFP(W)    ;;Yes, get old tail pointer
         DPB REG,[MLO,,MEMBLT(TEMP)]    ;;Add new one onto end of list
        ELSE.
         HRRM REG,MSBUFP(W)     ;;No, make new buffer head of list
        ENDIF.
        HRLM REG,MSBUFP(W)      ;;New buffer is tail in any event
        SETZM TEMP
        DPB TEMP,[MLO,,MEMBLT(REG)]     ;;Indicate end of list
        AOS MSNBOL(W)           ;;Increment count of buffers on list
TERMIN

DEFINE MTDEQB REG,TEMP=TT
        HRRZ REG,MSBUFP(W)      ;;Get head of buffer list
        HLRZ TEMP,MSBUFP(W)     ;;Get tail
        CAMN REG,TEMP           ;;Tail == head?
        IFSKP.
         LDB TEMP,[MLO,,MEMBLT(REG)]    ;;No, get next buffer on list
         HRRM TEMP,MSBUFP(W)    ;;Make it the new head of list
        ELSE.
         SETZM MSBUFP(W)        ;;Only one buffer, list is now empty
        ENDIF.
        SOS MSNBOL(W)           ;;Decrement count of buffers on list
TERMIN

IFN TM03S,[
;Macros for testing various status bits as set up by MGGXPT and friends
IRP OP,,[NN,NE,NA,O,OE,ON,OA,Z,ZE,ZN,ZA,C,CE,CN,CA]
  DEFINE TT!OP REG,#MSK
    ...TSF==0
    IFSE REG,CS1,[
        TL!OP I,MSK
        ...TSF==-1
        ]
    IFSE REG,CS2,[
        TR!OP I,MSK
        ...TSF==-1
        ]
    IFSE REG,FS,[
        TL!OP J,MSK
        ...TSF==-1
        ]
    IFSE REG,ERR,[
        TR!OP J,MSK
        ...TSF==-1
        ]
    IFE ...TSF,.ERR Invalid register name REG given in TTxxx macro
  TERMIN
TERMIN
];IFN TM03S
\fSUBTTL MAG TAPE OPEN ROUTINE

;       C/      MODE,,DEV
;       D/      MODE (ROT 1) 4.9=1=>OUTPUT
;       I/      DEVICE NUMBER
;       R/      IOCHNM WORD POINTER

MAGTO:  SKIPL W,I               ;Get device
         CAIL W,NMTCS           ;Too big?
          JRST OPNL1            ;No such device
        MOVSI T,%MAREW
        TDNE T,MSRAC(W)         ;Rewinding?
         PUSHJ P,UFLS           ;Yes, wait for completion
        CONO PI,CLKOFF          ;Don't want transport status changed under me
        SKIPL MTUSE(W)          ;See if we are the first opener
        IFSKP.                  ;First opener. Initialize database for device
         SETZM MSBUFP(W)        ;Indicate no buffers on chain
         SETZM MSNBOL(W)        ;Another way of saying above
         SETZM MSMPRC(W)        ;Buffer words remaining
         SETZM MSMPRP(W)        ;Pointer to buffers
         SETOM MTMDN(W)         ;No buffer at MP level
         SETOM MGCABN(W)        ;No buffer owned by PI code
         SETZM MSRAC(W)         ;Initialize transport software status word
         MOVEI A,2
         MOVEM A,MTCEFW(W)      ;Number of EOF's written
         MOVSI A,%MANWT
         IORM A,MSRAC(W)        ;Indicate nothing written on tape
        ELSE.                   ;Not first opener. Check legality of this open
         CAME U,MTUSR(W)        ;Same user as previous open?
          JRST OPNL10           ;Different user, report error
         MOVE B,D               ;Check direction of open
         EQV B,MSCRW(W)         ;Same as previous direction?
         SKIPL B                ;Yes, OK
          JRST OPNL2            ;No, wrong direction
        ENDIF.
        MOVEM U,MTUSR(W)        ;Store user
        SETZM MSCRW(W)          ;Indicate read until found to be otherwise
        TLNE C,1                ;Read or write?
         SETOM MSCRW(W)         ;Indicate write
        AOS MTUSE(W)            ;Indicate 1 more user
        PUSHJ P,SOSSET
            MTUSE(W)            ;SOS if PCLSR'd
        CONO PI,CLKON           ;Let um (em?) get me (who's em?)
        PUSHJ P,MTSTAT          ;Get transport status in standard form
        MOVE A,MSRAC(W)
        TLNE A,%MAERR           ;PI error means device not there
         JRST MTODNP            ;Go report error
IFN TM03S,[
        TTNN FS,%TMSFP          ;Formatter present?
         JRST MTODNP            ;No, can't win
                                ;Should check for slave present too.
]
IFN TM10P,[
        TXNN J,%T1STH           ;Transport hung, by chance?
         JRST MTOW1             ;No, proceed
        TXNN J,%T1SRW           ;OK if rewinding
         JRST OPNL7             ;Device not working
]
MTOW1:  SKIPN MSCRW(W)          ;Writing?
         JRST MTOW2             ;No...
IFN TM10P,TXNE J,%T1SWL         ;Yes. Write locked?
IFN TM03S,TTNE FS,%TMSWL
         JRST OPNL26            ;Yes, device writelocked error
IFN TM10P, TXNN J,%T1SET        ;At EOT?
IFN TM03S, TTNN FS,%TMSET
          JRST MTOW2            ;No
        MOVSI A,%MAETW+%MAERR   ;If write and EOT, make .IOT give IOC error,
                                ;  but let open win
        IORM A,MSRAC(W)

MTOW2:  TXNE C,%MMDEN           ;Density specified explicitly?
         JRST MTOW3             ;Yes, go check for validity
IFN TM10P,MOVEI A,1             ;No, pick one. Use 800 for TM10
IFN TM03S,MOVEI A,2             ;Use 1600 for TM03
        DPB A,[.BP %MMDEN,C]    ;Set value
        JRST MTOW4              ;Done and assumed correct

MTOW3:  LDB A,[.BP %MMDEN,C]    ;Get density from open
IFN TM10P,[
        CAIE A,1                ;800 is the only currently OK speed for TM10
         JRST OPNL12
 IFN 0,[
;You need something like this if you arrange to allow non-800 TM10 speeds
        TXNN C,%MM32B           ;32-bit compatible mode requested?
         JRST MTOW4             ;No, core dump
        CAIN A,1                ;Density specified as 800?
         JRST MTOW4             ;Yes, we can do that
        JRST OPNL12             ;32-bit and not 800BPI, controller can't do it
 ]
];IFN TM10P
IFN TM03S,[
        CAIN A,3                ;Specified 6250?
         JRST OPNL12            ;Yep, loser. Else OK
]

;Here on successful open.
; Set up CONO or select word, IOCHNM word, blocksize
;
MTOW4:  PUSHJ P,LSWDEL          ;Release MTUSE switch
IFN TM10P,[
        MOVEI A,MTCCHN_3        ;Start building CONO word. Set control PI level
IFN TM10A,TRO A,1               ;Add in data PI level for non-DF10 controller
        LDB B,[.BP %MMDEN,C]    ;Get density from open
        CAIE B,1                ;800 BPI
         BUG INFO,[ILLEGAL TM10 TAPE SPEED SETTING, USING 800BPI]
        MOVEI B,%T1D80          ; Yep.  
        DPB B,[.BP %T1CDS,A]    ;Set density field of CONO word
        TXNN C,%MM32B           ;32-bit mode specified?
         TXO A,%T1CCD           ;No, set core dump mode in CONO
        TXNN C,%MMEP            ;User wants even parity?
         TXO A,%T1COP           ;No, set odd parity
        DPB W,[.BP %T1CNU,A]    ;Set unit number field of CONO
        MOVEM A,MTCONO(W)       ;Save assembled CONO word
];IFN TM10P
IFN TM03S,[
        MOVE A,W                ;Get unit number being initialized
        TXNN C,%MM32B           ;User asked for industry compatible?
        IFSKP.                  ;Yes...
         MOVEI B,4              ;Set word-to-frame conversion factor
         MOVEM B,MTWTFC(W)
         MOVEI B,%TMFIC         ;Set mode in budding select word
        ELSE.                   ;Core dump...
         MOVEI B,5              ; takes 5 tape frames per word
         MOVEM B,MTWTFC
         MOVEI B,%TMFCD         ;Set CD format in select word
        ENDIF.
        DPB B,[.BP %TMTFS,A]    ;Set format in select word
        TXNE C,%MMEP            ;User wants even parity?
         TXO A,%TMTEP           ;Yes, set even parity flag
        LDB B,[.BP %MMDEN,C]    ;Get density from open  
        CAIE B,1                ;800 BPI specified?
         SKIPA B,[%TMD16]       ;Anything else, use 16
          MOVEI B,%TMD08        ;800, use that
        DPB B,[.BP %TMTDS,A]    ;Set density in select word
        MOVEM A,MTSELW(W)       ;Set select word for this unit
];IFN TM03S
        LDB B,[.BP %MMRSZ,C]    ;Get record size from open call
        TRC B,7                 ;Convert to power of two
        MOVEI A,10              ;Minimum record size is 10 (8.) words 
        LSH A,(B)               ;Blocksize = minimum * 2^power
        MOVEM A,MTBLKS(W)       ;Save blocksize in words
        LDB A,[.BP <%MMBLK\%MMIMG>,C]
                                ;Use unit/block and ascii/image bits as index
        HLR C,MTOPTB(A)         ;Get input dispatch routine from table
        TLNE D,400000           ;Remember D? Skip if user opened in input mode
         HRR C,MTOPTB(A)        ;OK, get output dispatch routine instead
        MOVEM C,(R)             ;Save routine in IOCHNM word
        DPB W,[MTXP(R)]         ;Set transport number in IOCHNM word
        JRST POPJ1              ;Skip return means success

;Here if device is not present
MTODNP: SETZM MSRAC(W)  ;Too bad. Clear status word and report error
        JRST OPNL1


;Table of I/O routines
;
MTOPTB: MTUAIX,,MTUAOX          ;Unit Ascii
        MTBIX,,MTBOX            ;Block Ascii
        MTUIIX,,MTUIOX          ;Unit Image
        MTBIX,,MTBOX            ;Block Image

\f

SUBTTL MAG TAPE CLOSE ROUTINES

;MTOCL - CLOSE TAPE OPEN FOR OUTPUT

MTOCL:  LDB W,[MTXP(R)]         ;Set up transport number
        SOSL MTUSE(W)           ;Decrement transport use counter
         POPJ P,                ;Not only channel open, all done
        AOS MTUSE(W)            ;Consistant state in case PCLSR'd
        MOVSI A,%MAERR
        TDNE A,MSRAC(W)         ;See if error has occurred
         PUSHJ P,MTOCL3         ;Yes, clean up a few things

        SKIPL MTMDN(W)          ;Is there a partially processed buffer?
         PUSHJ P,MTWBFD         ;Yes, write it to tape

        MOVEI B,MGMEOT          ;Queue a "Write EOT" command to PI level
        PUSHJ P,MTCMD
        SKIPLE MSCMDC(W)
         PUSHJ P,UFLS           ;Wait till done. 
        MOVEI A,1
        MOVEM A,MGEOFR(W)
        SKIPGE MTMDN(W)         ;Active buffer at MP level?
        IFSKP.
         MOVE A,MTMDN(W)
         BUG PAUSE,[MT: MP BUF REMAINS AT CLOSE],OCT,A
         PUSHJ P,MEMR
        ENDIF.
        SKIPGE MGCABN(W)                ;Active buffer at PI level?
        IFSKP.
         MOVE A,MGCABN(W)
         BUG PAUSE,[MT: PI BUF REMAINS AT CLOSE],OCT,A
         PUSHJ P,MEMR
        ENDIF.
        SKIPN MSNBOL(W)         ;Any buffers on buffer queue?
        IFSKP.
         BUG PAUSE,[MT:],DEC,MSNBOL(W),[BFRS QUEUED AT CLOSE]
         PUSHJ P,MTCBFF
        ENDIF.
        SETOM MTUSE(W)          ;Nobody is using this transport
        SETOM MTUSR(W)          ;No user associated with this transport
        SETZM MSRAC(W)          ;reset transport software status word
        POPJ P,

MTOCL3: SKIPL A,MTMDN(W)        ;Have a buffer active at MP level?
         PUSHJ P,MEMR           ;Flush it if so
        SETOM MTMDN(W)
        SETZM MSMPRC(W)         ;Say no words left in current buffer
        POPJ P,
\f
;Close routine for MT open for input

MTICL:  LDB W,[MTXP(R)]         ;Set up channel data pointer
        SOSL MTUSE(W)           ;Last user?
         POPJ P,                ;No, nothing to do
        AOS MTUSE(W)            ;Yes, save state for possible PCLSR
        MOVEI T,1               ;This crock is because we want to allow
        CAMGE T,MSCMDC(W)       ; one outstanding command if rewinding
         PUSHJ P,UFLS           ;Wait till one or less outstanding command
        MOVE T,MSRAC(W)         ;Get transport software status
        TLNE T,%MAREW           ;Is it rewinding?
        IFSKP.
         SKIPLE MSCMDC(W)       ;No, wait till no outstanding commands
          PUSHJ P,UFLS
        ENDIF.
        SKIPGE MGCABN(W)        ;Any PI-level buffers left?
        IFSKP.
         MOVE A,MGCABN(W)        
         BUG PAUSE,[MT: PI INPUT BUF LEFT AT CLOSE],OCT,A
         PUSHJ P, MEMR
        ENDIF.
        PUSHJ P,MTRBD           ;Release any MP-level buffers
        SETOM MTUSR(W)          ;Reset user identifier
        PUSHJ P,MTCBFF          ;Free some buffers ?whose+++
        SOS MTUSE(W)            ;Decrement use count
        MOVE T,MSRAC(W)         ;Get transport software status again
        TLNE T,%MAREW           ;Are we rewinding?
         JRST MTICL2            ;Yes, don't have to skip to EOF
        MOVSI A,(%MMNSE)
        TDNE A,(R)              ;Check if user wants skip to EOF
         JRST MTICL2            ;No, forget it
        MOVSI A,%MAMSO
        TDNN A,MSRAC(W)         ;Has tape moved at all since open?
         JRST MTICL2            ;No...
        SKIPE MGEOFR(W)         ;
         JRST MTICL2            ;Note that this disposes of a read-ahead EOF.
        PUSHJ P,MTSTAT
IFN TM10P,[
        MOVE B,MGCMTS(W)
        TXNE B,%T1SBT           ;BOT?
         JRST MTICL2
]
IFN TM03S,[
        TTNN FS,%TMSOL          ;Still online?
         JRST MTICL2            ;No, can't very well skip to EOF
        TTNE FS,%TMSBT
         JRST MTICL2
]
        MOVEI B,MGSPFF          ;Space forward to end of file
        PUSHJ P,MTCMD
        SKIPLE MSCMDC(W)        ;Wait till command done
         PUSHJ P,UFLS

MTICL2: MOVSI T,%MAREW
        ANDM T,MSRAC(W)         ;Clear all software status except rewinding
        POPJ P,                 ;Done

;Free a chain of IO buffers pointed to by MSBUFP(W)
; Count of buffers is in MSNBOL(W)
;
MTCBFF: SKIPN MSNBOL(W)         ;Any buffers on chain?
         POPJ P,                ;No, fine
        DO.
         HRRZ A,MSBUFP(W)       ;Yes, get pointer
         LDB T,[MLO,,MEMBLT(A)] ;Get pointer to next buffer
         HRRM T,MSBUFP(W)       ;Write that in chain header
         PUSHJ P,MEMR           ;Return buffer to IO pool
         SOSLE MSNBOL(W)        ;Any more to do?
          JRST TOP.             ;Yes, loop back for more
        ENDDO.
        SETZM MSBUFP(W)         ;Zero buffer list pointer
        POPJ P,

\f

SUBTTL MAG TAPE INPUT .IOT ROUTINES

        SKIPA B,[SIOKT]
MTUAI:   MOVEI B,CHRKTI         ;Unit ASCII input
        MOVE E,[440700,,5]
        JRST MTREAD

        SKIPA B,[SIOKT]
MTUII:   MOVEI B,CHRKTI         ;Unit image input
        MOVE E,[444400,,1]
        JRST MTREAD

MTBI:   MOVE E,[444400,,1]      ;Block input
        MOVEI B,BLKT

MTREAD: LDB W,[MTXP(R)]         ;W <= Transport number
        PUSHJ P,MTIECK          ;Check for tape errors first
        MOVEM P,MTPSAV(W)       ;Save P for EOF return
        JSP B,(B)               ;IO Routine. BLKT,CHRKT,SIOKT
            MSMPRP(W)           ;Pointer to next word
            MSMPRC(W)           ;Count of words remaining
            SETZ MTRBG          ;Get new buffer (SETZ for CHRKT return on EOF)
            MTRBD               ;Discard buffer
            JRST 4,.            ;Unused
            PUSHJ P,MTRBFW      ;Code to wait for new buffer from PI level

;Get a new buffer for I/O code.
; This routine assumes that there is a buffer ready to get
; (i.e. MTRBFW was called)
;
MTRBG:  SKIPG MSNBOL(W)         ;Any buffers on list?
         JRST MTRBG3            ;No, must be error or EOF
        CONO PI,UTCOFF          ;Stop I/O for a bit
        MTDEQB TT,A             ;Dequeue buffer into TT using A as temp
        MOVEM TT,MTMDN(W)       ;Remember buffer active at MP level
        CONO PI,UTCON           ;Turn I/O back on
        LDB J,[MWC,,MEMBLT(TT)] ;Get word count from buffer
        MOVEM J,MTBLKS(W)       ;Save for .MTAPE 13
        LSH TT,10.              ;Convert buffer number into address
        JRST SIOBGX             ;TT/address, J/word count /E unchanged

;Here if no buffer ready, error or EOF assumed
;
MTRBG3: SKIPL MSRAC(W) .SEE %MAEOF      ;EOF flag set in transport status?
        IFSKP.
         MOVSI T,%MAEFA         ;The EOF is now no longer read-ahead
         ANDCAM T,MSRAC(W)      ;So remember that fact
         JRST POPJ2             ;Double skip to tell I/O code about EOF
        ENDIF.
        PUSHJ P,MTIECK          ;Not EOF. Check for error conditions
        BUG HALT,[TAPE READ BUFFER VANISHED] ;No error, shoulda been a buffer
\f
;MAG TAPE READ BUFFER DISCARD ROUTINE
MTRBD:  SKIPGE A,MTMDN(W)       ;Have an active MP buffer?
         JRST MOVTWJ            ;Set up T for buffer wait, return
        CONO PI,UTCOFF          ;Stop IO for a bit
        SETOM MTMDN(W)          ;No active MP buffer
        SETZM MSMPRC(W)         ;No data in nonexistant buffer
        LDB TT,[MSEOFP,,MEMBLT(A)]      ;Get EOF flag from PI level
        PUSHJ P,MGMEMR          ;Return buffer, enable UTC
        JUMPN TT, [ MOVSI A,%MAEOF      ;EOF seen?
                    IORM A,MSRAC(W)     ;Record EOF in software status
                    JRST .+1 ]
MOVTWJ: MOVE T,W                ;T gets transport number for bfr wait UFLS
        POPJ P,                 ;Also MTRBG, MTRBFW rely on this setting T


;MAG TAPE READ WAIT FOR DATA ROUTINE
; Called under a UFLS by system IO code to wait for data to arrive.
; Note T, not W, has transport number. T must be set up by some
; previous routine
;
MTRBFW: MOVE TT,MSRAC(T)        ;Get software status of transport
        TLNN TT,%MAEOF\%MAERR   ;PI code reports EOF or error?
        SKIPLE MSNBOL(T)        ;Or are any buffers available for reading?
         JRST POPJ1             ;SOme interesting condition, unhang
        TLNE TT,%MARAC          ;Have we asked for a tape read yet?
         POPJ P,                ;Yes, nothing to do but wait, wait, wait
        PUSH P,W                ;This being done under a UFLS. only T good
        PUSH P,B
        MOVE W,T                ;Set up transport number in usual place
        MOVEI B,MGREAD          ;What we want the PI level to do
        MOVEI T,MSCBL           ;Make sure that there is room in command list
        CAMG T,MSCMDC(W)        ;If there is room,
        IFSKP.                  ; we will request a read operation
         MOVSI TT,%MARAC
         IORM TT,MSRAC(W)       ;Read is active now, or will be shortly
         PUSHJ P,MTCMD1         ;Queue up command request for PI level
        ENDIF.                  ;If no room for command, all we can do is wait
        MOVE T,W                ;Fix up T for UFLS
        POP P,B                 ;Clean up everything else
        POP P,W
        POPJ P,
\f
SUBTTL MAG TAPE OUTPUT .IOT ROUTINES

        SKIPA B,[SIOKT]
MTUAO:   MOVEI B,CHRKT          ;Unit ASCII output
        MOVE E,[440700,,5]
        JRST MTWRIT

        SKIPA B,[SIOKT]
MTUIO:   MOVEI B,CHRKT          ;Unit image output
        MOVE E,[444400,,1]
        JRST MTWRIT

MTBO:   MOVE E,[444400,,1]      ;Block output
        MOVEI B,BLKT

MTWRIT: LDB W,[MTXP(R)]         ;Get transport number
        PUSHJ P,MTIECK          ;Check for tape errors first
        HRLZI A,%MAETW
        TDNE A,MSRAC(W)         ;PI code think it hit EOT?
         JRST IOCER9            ;Yep, go lose
        JSP B,(B)
            SETZ MSMPRP(W)      ;Pointer to next word
            MSMPRC(W)           ;Count
            SETZ MTWBFG         ;Get new buffer
            MTWBFD              ;Write out buffer to tape
            JRST 4,.
            TRNA                ;No wait for buffer routine needed
\f
;MAG TAPE WRITE - BUFFER GET ROUTINE

MTWBFG: PUSHJ P,MTIECK          ;Check for tape errors
        PUSHJ P,TCALL           ;Turn off UTC
            JRST IOMQ           ;Try to get buffer
         POPJ P,                ;Return noskip if no buffers available
        MOVEM A,MTMDN(W)        ;Store active buffer number
        MOVEI T,MUMGB
        DPB T,[MUR,,MEMBLT(A)]  ;Tell world that it is a mag tape buffer
        DPB W,[MSCHN,,MEMBLT(A)] ;Store channel number in buffer header
        SETZM TT
        DPB A,[121000,,TT]      ;Convert block number in A to address in TT
        MOVE J,MTBLKS(W)        ;Get block size of write
        JRST SIOBGX

;MAG TAPE WRITE - BUFFER FINISHED ROUTINE
; General IO code has filled a buffer or otherwise finished with it.
; Queue the buffer for writing if there is anything in it.

MTWBFD: PUSHJ P,MTIECK          ;Check for tape errors
        SKIPGE A,MTMDN(W)       ;Have an active buffer?
         POPJ P,                ;No, nothing to do
        MOVEI T,MSCBL           ;See if there is any room in command list
        CAMG T,MSCMDC(W)
         PUSHJ P,UFLS           ;Wait for room in command list
        MOVE T,MTBLKS(W)        ;Get blocksize we are writing
        SUB T,MSMPRC(W)         ;Subtract number of words remaining in buffer
        CONO PI,UTCOFF          ;Lock up while frobbing buffer lists
        SETOM MTMDN(W)          ;Clear active buffer
        SETZM MSMPRC(W)         ;Clear free word in buffer count
        JUMPE T,MEMR            ;Nothing in buffer, just return block
        DPB T,[MWC,,MEMBLT(A)]  ;Store word count
        MTENQB A                ;Queue buffer on to-PI list
        CONO PI,UTCON           ;Finished mucking with buffer list
        PUSH P,B
        MOVEI B,MGWRIT          ;Issue a write request to PI level
        PUSHJ P,MTCMD
        MOVSI B,%MANWT
        ANDCAM B,MSRAC(W)       ;Note that we have written something to tape
        SETZM MTCEFW(W)         ;Note no EOF's written at end of tape
        JRST POPBJ              ;Restore B and return
\f
SUBTTL MTCMD - GIVE COMMAND TO PI LEVEL

;PUSHJ P,MTCMD
        ;RH(W) has transport number
        ;RH(B) has address of PI level routine to execute

MTCMD:  MOVEI T,MSCBL           ;Pending command list length
        CAMG T,MSCMDC(W)        ;Count of commands currently in list
         PUSHJ P,UFLS           ;Wait for room in pending command list 
        CONO PI,UTCOFF          ;Grab machine, keep count accurate
MTCMD1: MOVE T,MTCMBP(W)        ;Get pointer to next slot in command list
        AOBJN T,MTCMD2          ;Increment slot and check for wraparound
         SUB T,[MSCBL,,MSCBL]   ;Reached end of list, ring it
MTCMD2: MOVEM B,(T)             ;Store new command
        MOVEM T,MTCMBP(W)       ;Store new pointer
        AOS MSCMDC(W)           ;Indicate one more command in list
        JRST MSTRTR             ;Go start up PI routine

SUBTTL MTIECK - CHECK FOR IOC ERROR

;PUSHJ P,MTIECK
        ;Returns +1 if no error
        ;Gives IOC error to user if error - never returns.

MTIECK: PUSH P,A
        MOVE A,MSRAC(W)         ;Get transport software status
        TLNN A,%MAERR           ;PI level report an error?
         JRST POPAJ             ;No, all is OK
        SKIPLE MSCMDC(W)        ;Wait for PI level to finish cleaning up
         PUSHJ P,UFLS           ; before throwing away buffers
        SKIPL A,MTMDN(W)        ;Have an active MP-level buffer?
         PUSHJ P,MEMR           ;Yes, throw it away
        SETOM MTMDN(W)          ;No active MP buffer
        SETZM MSMPRP(W)         ;No place to get/put next character
        SETZM MSMPRC(W)         ;No room to do it anyway
        PUSHJ P,MTCBFF          ;Free any buffers waiting for MP processing
        POP P,A
        MOVE T,MGCMTS(W)        ;Get transport status data from PI level
IFN TM10P,[
        TRNE T,%T1STH\%T1SIO    ;Transport hung or illegal operation?
         JRST IOCER1            ;Yes, report device error
        TRNE T,%T1SPE\%T1SRC\%T1SRL\%T1SDL\%T1SBT       ;Gruesome errors
         JRST IOCER3            ;Report irrecoverable data error
        TRNE T,%T1SET           ;(Real) End of Tape?
         JRST IOCER9            ;Device Full error
];IFN TM10P
IFN TM03S,[
        MOVE I,MGCMTC(W)        ;Get controller transport status from PI level
        MOVE J,MGCMTS(W)
        TTNE CS1,%TM1MP         ;Control bus parity error?
         JRST IOCER1
        TTNN CS1,%TM1TE         ;Transfer error? Could be TM03 or RH11
        IFSKP.
         TTNE CS2,%TM2DL\%TM2UP\%TM2NF\%TM2NM\%TM2PE\%TM2MT\%TM2MP
          JRST IOCER1           ;Non-data errors
         TTNN FS,%TMSES         ;Formatter error?
         IFSKP.
          TTNE ERR,%TMEUS\%TMECT\%TMENX\%TMEMD\%TMEFS\%TMEMC\%TMERM\%TMEIR\%TMEIF
           JRST IOCER1          ;Fatal formatter errors
          TTNE ERR,%TMECE\%TMECS\%TMEFC\%TMENG\%TMEFL\%TMEIC
           JRST IOCER3          ;Non-recoverable data errors
         ENDIF.
        ENDIF.
        TTNE FS,%TMSET          ;End of tape?
         JRST IOCER9
];IFN TM03S
        MOVE A,MGEOFR(W)        ;Check for logical EOT
        CAIL A,2                ;Read two EOF's since last record?
         JRST IOCER9            ;Yes, report EOT
        JRST IOCER3             ;No, give irrecoverable data error for now
\f
SUBTTL MAG TAPE .STATUS ROUTINE
;Building a status word in D.
;Routine sets:
; 1.7-1.9 open modes
; 2.3 BOT
; 2.4 EOT
; 2.5 9 track (0 = 7 track)
; 2.6 IBM mode (0 = coredump)
; 2.7 Transport idle (no pending command)
; 2.8 EOF (last thing seen was a tape mark)
;
STAMTC: 
;Open modes
        LDB W,[MTXP(R)]         ;Get transport number
        DPB A,[60300,,D]        ;Open mode
        PUSHJ P,MTSTAT          ;Get tape status from transport
;EOT?
        LDB A,[.BP %MAETW_22,MSRAC(W)]  ;EOT on write
        LDB B,[.BP %MAETR_22,MSRAC(W)]  ;EOT on read
        IOR A,B
        DPB B,[140100,,D]       ;Tape at EOT?
IFN TM10P,[
;7 or 9 track drive?
        LDB A,[20100,,J]        ;Get 7/9 track bit
        TRC A,1
        DPB A,[150100,,D]       ;7 or 9 track drive
        .ERR Missing TM10 .STATUS code at STAMTC
]
IFN TM03S,[
;A bunch of new stuff. BOT?
        SETZ A,
        TTNE FS,%TMSBT          ;Transport is at BOT?
         SETO A,
        DPB A,[130100,,D]       ;BOT.
;7 or 9 track drive?
        SETOM A                 ;TM03 is always 9-track
        DPB A,[150100,,D]       ;7 or 9 track drive
;Core dump or 32 bit mode?
        MOVE A,MTWTFC(W)        ;Get word to frame conversion. 4 or 5
        TRC A,1                 ;Flip last bit. Last bit now on iff 32bit mode
        DPB A,[160100,,D]       ;Sorry.
;Formatter busy?
        SETO A,
        SKIPLE MSCMDC(W)        ;Idle if no pending commands
         SETZ A,
        DPB A,[170100,,D]
;EOF last thing seen?
        SETZ A,
        TTNE FS,%TMSTM          ;Last thing seen was a tape mark?
         SETO A,
        DPB A,[200100,,D]       ;EOF. 
];IFN TM03S
        POPJ P,

;RCHST ROUTINE FOR MAG TAPE

RCHMGT: HLRZ E,(R)              ;Get open mode from IOCHNM word
        LDB J,[MTXP(R)]         ;Get the mag tape drive number
        MOVSI J,'MT0(J)         ;Return that drive's device name
        TRZ E,(.BM MTXP)        ;Clear drive # field in OPEN modes
        JRST POPJ1              ;Skip so that J overrides built-in device name

\f
SUBTTL MAG TAPE PI LEVEL

;Request magtape interrupt from MP-level software
; Must be called with I/O interrupts off (CONO PI,UTCOFF)
; This is called every 1/2 second by the ITS slow clock routine
; 
MSTRTR: SETZM MGTBZY            ;No busy tapes, flag software interrupt
        CONO PI,MTCRQ           ;Request interrupt on magtape channel
        CONO PI,UTCON           ;Reenable IO interrupt system
        POPJ P,                 ;That is all

;Handle tape interrupt requested by software or other nonspecific cause
; Get here via non-vectored MTCCHN interrupt on the KS
;
MGSBRK: AOS MGTBZY              ;Note interrupt level is busy
        SETOM MGSFTI            ;Note software interrupt in progress
        MOVEI B,NMTCS-1         ;Loop over all transports
        SKIPG MSCMDC(B)         ;Any commands in command list?
MGSBK1:  SOJGE B,.-1            ;No, try next transport
        SKIPGE B                ;Found command or finished scan. Which?
         JRST MGSBK2            ;Finished scanning. Go check other things
        MOVE W,B                ;Have a command. Set up transport number
        PUSH P,B                ;Save B over call to command routine
        MOVSI B,%MACTH
        TDNN B,MSRAC(W)         ;Core allocator saying go away?
         PUSHJ P,MGXGO          ;No, go start requested routine
        POP P,B                 ;Restore transport count
        JRST MGSBK1             ;Loop back for another transport

MGSBK2: SETZM MGSFTI            ;Clear software interrupt flag
        JRST MGEX               ;That's all for now
;This probably should check for lost IE bits on TM03

;Handle interrupt caused by specific hardware conditions
; Get here via vectored interrupt on the KS
;

IFN TM10P,[
; A - result of CONI MTC,
; C - result of CONI MTS,
;
MGHBRK: SKIPGE W,MGUNIT         ;Get unit we are expecting interrupt on
         JRST MGUBRK            ;None? Probably MP level bailed out. Punt.
        LDB B,[MUNITF,,A]       ;Get unit that controller is squacking about
        CAME W,B                ;Same unit?
         BUG HALT,[MT PI CODE LOST TRANSPORT]
        MOVE J,C
        PUSH P,[MGEX]           ;Cause POPJ P, in handler to dismiss interrupt
IFN TM10B,[
        TXNE C,%T1SCP\%T1SNM\%T1SDP     ;Check for DF10 errors
         JRST MGERR             ;Yes, go to error routine
];TM10B
        TXNE C,%T1SIO           ;Illegal operation error?
         JRST MGERR             ;Yes, go to error routine
        JRST MGXGO              ;No, go handle interrupt

;Here to unbreak on unexpected hardware interrupt
;
MGUBRK: LDB W,[MUNITF,,A]       ;Who's the loser, anyway
        MOVE B,MTCONO(W)        ;Get prototype CONO word for that transport
        CONO MTC,(B)            ;Select offending unit
        CONO MTS,31             ;Clear interrupt, DF10, stop any op in progress
        JRST MGEX               ;Go dismiss interrupt
];IFN TM10P

IFN TM03S,[
;Check for active unit. If none, go directly to inactive slave
;polling code. If active unit,check that controller is talking about
;this unit, then jump to its routine (MGXGO). When that finishes,
;see if controller is still showing attention, and check status
;of other transports if so.
;
;Well, almost.

        EBLK
MGHBRK: 0
        BBLK
        JSR UTCSAV              ;Save AC,s set up interrupt P PDL
        AOS MGTBZY              ;Note interrupt level is alive
        SKIPGE W,MGUNIT         ;Some transport waiting for an interrupt?
         JRST MGNOUW            ;Nope, either Slave Status Change or lossage
        IORDI B,%TMTC           ;Get transport the TM03 is thinking about
        ANDI B,7
        CAME B,W                ;Same as the one we were waiting for?
         BUG HALT,[MT PI CODE LOST TRANSPORT]
        PUSHJ P,MGXGO           ;Go jump into this unit's handler

MGNOUW:
IFN NMTCS-1,[
.ERR Missing multi-transport code at MGNOUW!
If more than one unit, have to see if this is an interrupt caused by a
SSC (slave status change), and if so poll all the inactive units and
update their software status (rewinding, on/off line, etc.) With only
one transport we currently avoid this by keeping the unit active
(MGUNIT set) as long as it is doing *anything*, and giving it all the
hardware interrupts. See rewind code, too.
];IFN NMTCS-1
        JRST MGEX               ;Go dismiss interrupt
];IFN TM03S
\f
;Interrupt level control flow
;
; Each transport maintains the current state of its PI-level action
; routines on a seperate (per-transport) PDL with its SP in Q. This
; allows you to save the current state, dismiss the interrupt, and
; resume where you left off when the next interrupt for this transport
; arrives.
; 
; Subroutine linkage between routines handling a per-drive PI-level
; action is with PUSHJ Q,xxx and POPJ Q,
;
; The MP level queues commands for the PI level to process on a per-
; transport queue at MGSBx (x=unit number)
;
; Ths general interrupt code transfers to the per-drive actions by
; jumping to MGXGO, which will load Q from the saved state of the
; current drive and start up whatever it finds there. This may be
; the MGNCMD routine, which will start a new command, or it may be
; the middle of an in-progress PI-level command handler.
;
; PI-level action routines can relinquish control in several ways:
;
;  PUSHJ Q, CPOPJ will dismiss the current interrupt, arranging for
;  control to return to the instruction following the PUSHJ when the
;  next interrupt for this unit occurs.
;
;  JRST MGOVER will dismiss the current interrupt, arranging for the
;  currently executing subroutine to be restarted "from the top" when
;  the next interrupt for this unit occurs.
;
;  A simple POPJ P, will dismiss the current interrupt, arranging for
;  the routine that called this one to be started at the point immediately
;  after the call when the next interrupt comes in. This is generally not
;  useful except from first-level action routines, where a POPJ P, will
;  indicate that you have finished handling the current command and cause
;  the next interrupt to fetch and start execution of a new command from the
;  queued command list by transferring to MGNCMD. Got that?

;Transfer control to whatever the per-transport code wants to do.
;
MGXGO:  MOVE Q,MGQDLP(W)        ;Getsaved Q PDL pointer for current transport
        PUSHJ P,QPOPJ           ;"Return" to whatever is on top of Q PDL,
                                ; arranging for POPJ P, to return to here

        MOVEM Q,MGQDLP(W)       ;Save current Q PDL for next time
        POPJ P,                 ;Return, dismissing this interrupt

;Dismiss interrupt, arranging for next interrupt to restart routine
; we are currently executing (rather than either continuing here or
; starting a new command)
;
MGOVER:
IFN TM10P,[
        CONSZ MTS,%T1STH\%T1SIO\%T1SCE  ;Tape hung/ill op/DF10 error, 
         JRST MGERR             ; go handle error condition
]
        SOS (Q)                 ;Decrement address at top of Q PDL, now
                                ; points to PUSHJ Q, <us> instruction so
                                ; that we will get called again from MGXGO
                                ; at next interrupt dispatch
        POPJ P,                 ;Return to P PDL caller, dismissing interrupt


;This routine is always the last "command" in a transport command list
; Wraps the command list BP around the the beginning of the list,
; then gets and executes the next command.
;
MGRCV:  MOVNI A,MSCBL+1         ;Get negative length of command list
        ADDM A,MGCMBP(W)        ;Wrap command extraction pointer back to start
MGNCM1: ILDB B,MGCMBP(W)        ;Get new command from list
        JRST (B)                ;And jump to it

;This code is always the first (bottom) thing in a transport's Q PDL
; It is therefore executed whenever MGXGO transfers control to the
; Q PDL and there is no command in progress.
;
MGNCMD: AOBJN Q,MGNCM1          ;Got here w/ POPJ Q,. Fake PUSHJ to restore Q,
                                ; then go get the next command
        
        BUG                     ;Q PDL pointer clobbered

QPOPJ1: AOS (Q)
QPOPJ:  POPJ Q,

\f
;WAIT FOR JOB DONE BIT TO SET
; Called from PI-level command routines to wait for end of command.
; Called with PUSHJ Q,MGWTJD
;
; Returns +1 to caller if unusual termination
;         +2 to caller if operation terminated normally
; 
;       I,J contain tape status:
;        On TM10, I=CONI MTC,
;                 J=CONI MTS
;        On TM03S, I=%TMCS1,,%TMCS2 (controller status),
;                  J=%TMFS,,%TMERR (formatter status)

IFN TM10P,[
MGWTJD: CONI MTS,J              ;Get transport status
        TXNE J,%T1STH\%T1SIO    ;Transport hung or Illegal operation?
         JRST MGERR             ;Yes, job-done isn't ever going to get set
MGWJD1: CONI MTS,J              ;Get status again
        SKIPN MGJDTI            ;Is there a time out set?
        IFSKP.
         MOVE T,TIME            ;Yes, check it. Get current time
         CAML T,MGJDTI          ;Smaller than specified timeout time?
          JRST MGERR            ;No, lose
        ENDIF.
        TXNN J,%T1SJD           ;JOB-DONE bit set?
         JRST MGOVER            ;No, we want to wait for it
        CONI MTS,J              ;Job Done. Get status
        CONI MTC,I              ;Get CONI MTC
        MOVEM J,MGCMTS(W)       ;Save for MP level
        MOVEM I,MGCMTC(W)
IFN TM10B,[
        SKIPE MGWCW             ;Want to wait for control word?
         PUSHJ Q,MGWCWC         ;Check to see if it is written
        SETZM MGWCW             ;Clear wait-for-control-word request flag
]
        CONO MTS,30             ;Clear channel conditions
        MOVE B,MTCONO(W)
        CONO MTC,(B)            ;Release mtc, clear job done bit
IFN TM10B,[
        TXNE J,%T1SCP\%T1SNM\%T1SDP     ;Check for channel errors
         POPJ Q,                ;Channel error, return nonskip
]
        TXNE J,%T1STH\%T1SIO\%T1SPE\%T1SRC%\T1SRL\%T1SDL\%T1SBT
         POPJ Q,                ;Random other things, not necessarily errors
        JRST QPOPJ1             ;Success
];IFN TM10P
IFN TM03S,[
MGWTJD: 
MGWJD1: IORDI T,%TMCS1          ;Get controller status
        TXNN T,%TM1GO           ;Go bit still set?
         JRST MGWJD2            ;No, command is finished. Go check errors
        SKIPE T,MGJDTI          ;Is there a time out set? Get it if so.
         CAML T,TIME            ;Past timeout time
          JRST MGOVER           ;No timeout or not timed out yet, go wait
        JRST MGERR              ;Timed out. Go check transport

;Here if action has terminated. Set up status bits before returning
MGWJD2: HRLZ I,T                ;%TMCS1,,?
        IORDI T,%TMCS2
        HRR I,T                 ;I = %TMCS1,,%TMCS2
        IORDI J,%TMERR
        IORDI T,%TMFS
        HRL J,T                 ;J = %TMFS,,%TMERR - I,J now in standard form
        MOVEM J,MGCMTS(W)       ;Save for MP level
        MOVEM I,MGCMTC(W)
        TTNE CS1,%TM1MP         ;Massbus control parity error
         JRST MGERR             ;Who knows what the transport is doing
        TTNN CS1,%TM1TE         ;Controller error?
         TTNE FS,%TMSES         ;Formatter error?
          POPJ Q,               ;Yes, return +1 for closer examination
        JRST QPOPJ1             ;Success
];IFN TM03S

;Select the transport given by W
; Returns +1 with transport selected, status in I,J
; May dismiss and wait for a while first
;
MGGXPT: 
IFN TM10P,[
        CONSO MTS,%T1SNU        ;Can controller select new unit right now?
         JRST MGOVER            ;No, wait for it
        MOVE T,TIME
        ADDI T,10.*30.          ;Time out in 10. seconds
        MOVEM T,MGJDTI          ;Set up job-done timeout
        MOVEM W,MGUNIT          ;Note unit waiting for hardware interrupt
        MOVE B,MTCONO(W)        ;Get CONO word for new unit
        CONO MTC,MNOPIN(B)      ;NOP, but interrupt when new drive is ready
        PUSHJ Q,MGWJD1          ;Wait for job done
         JFCL                   ;Ignore any errors
        SETZM MGJDTI            ;No more timeout
        SETOM MGUNIT            ;Not waiting any more
        POPJ Q,                 ;Return to caller
];IFN TM10P
IFN TM03S,[
        IORDI T,%TMFS           ;Get current formatter status
        TXNN T,%TMSES\%TMSSC    ;Showing error or slave status change?
        IFSKP.                  ;Yes, clear errors before going ahead
         IOWRI W,%TMTC          ;Select slave
         MOVEI A,10.            ;Try 10 times to clear drive
         MOVEI B,%TMCLR
         DO.
          IOWRI B,%TMCS1        ;Write drive clear command
          IORDI T,%TMFS         ;Get status
          TXNN T,%TMSES         ;Still have error
           JRST ENDLP.          ;No, done
          SOJG A,TOP.           ;Retry up to 10 times
          JRST MGERR            ;Else give up
         ENDDO.
        ENDIF.
        MOVE T,MTSELW(W)        ;Get desired settings
        IOWRI T,%TMTC           ;Tell TM03
        MOVEI T,%TMNOP          ;You may need this to set status values
        IOWRI T,%TMCS1          ; but I'm not really sure
        IORDI T,%TMCS1
        PUSHJ Q,MGWJD2          ;Go set status registers appropriately
         JFCL                   ;Maybe should check non-existant slave?
        POPJ Q,
];IFN TM03S

;MGERR - HANDLE TAPE ERROR
;
;Called from PI level command routines which detect a tape or controller error
; Flags error in software status word, records error status in MGExxx.
; Flushes command in progress by resetting Q PDL to base.
; Flushes commands in PI-level command queue by resetting queue pointers.
; Flushes any buffers which might be queued for writing.
; Returns to P PDL, to wait for new commands.

MGERR:
IFN TM10P,[
        CONI MTS,MGEMTS         ;Get transport status for MP level analysis
        CONI MTC,MGEMTC
]
IFN TM03S,[
        IORDI T,%TMCS1          ;Get controller and transport status into
        HRLM T,MGEMTC           ; standard form
        IORDI T,%TMCS2
        HRRM T,MGEMTC
        IORDI T,%TMFS
        HRLM T,MGEMTS
        IORDI T,%TMERR
        HRRM T,MGEMTS
        MOVE I,MGEMTC           ;Get status to standard place for macros
        MOVE J,MGEMTS
];IFN TM03S
        MOVSI T,%MARAC          ;Read not active, for sure
        ANDCAM T,MSRAC(W)
        SETZM MSCMDC(W)         ;No commands active
        SETOM MGUNIT            ;Clear unit wait flag
        SETZM MGJDTI            ;No job-done timeout
IFN TM10B,[
        TXNE J,%T1SCP\%T1SNM\%T1SDP     ;Channel error?
         BUG PAUSE,[MTAPE: CHANNEL ERROR, STATUS=],OCT,J,[MICWA+1=],OCT,MICWA+1,[MIOWD=],OCT,MIOWD
];TM10B
IFN TM03S,[
        .ERR UBA errors? More gentle cleanup? 
        TTNE CS1,%TM1MP\%TM1TE  ;Cbus parity or transfer error?
         TTNE FS,%TMSES         ;And no formatter error?
          SKIPA                 ;Yes and yes (no) (what?). Controller error
           BUG INFO,[MTAPE: RH11 ERROR, STATUS=],OCT,MGEMTC,[TM STATUS=],OCT,MGEMTS
        TTNE FS,%TMSES          ;Formatter error?
         BUG INFO,[MTAPE: FORMATTER ERROR, STATUS=],OCT,MGEMTS
        PUSHJ P,TMINIC          ;Go reinit controller
];IFN TM03S
        SKIPL A,MGCABN(W)       ;Any buffers owned by PI routines?
         PUSHJ P,IMEMR          ;Yes, give them back to system
        SETOM MGCABN(W)         ;No PI buffer any more
        HRLZI B,%MAERR          ;Flag error detected by PI level
        IORM B,MSRAC(W)         ;Store in transport status word
        MOVE Q,[-MGQDLL,,MGQD0-1];Reset Q PDL to base of this unit's stack,
        MOVE T,MSLCTB           ; thus flushing whatever command is in progress
        IMUL T,W                ;Find offset to base of Q PDL for this unit
        ADD Q,T                 ;Add to prototype unit 0 QDP pointer,
        PUSH P,Q                ; and save it away
        MOVE Q,[-MSCBL-1,,MSCB0-1]      ;Get command list input pointer
        ADD Q,T                 ;Offset it to this unit's command queue,
        MOVEM Q,MTCMBP(W)       ;And save it as new MP (input) queue pointer
        MOVE Q,[4400,,MSCB0-1]  ;Get new command list output pointer
        ADD Q,T                 ;Offset correctly for this unit,
        MOVEM Q,MGCMBP(W)       ;And save as PI (output) command queue pointer
        MOVSI B,%MAREW          ;Does initting xport stop TM03 rewind?
        ANDCAM B,MSRAC(W)       ;Say not rewinding
        SKIPN MSCRW(W)          ;If reading,
         JRST POPQJ             ; we're done. Restore Q and exit
        SKIPN MSNBOL(W)         ;Writing. Any buffers on list?
         JRST POPQJ             ;No, restore Q and exit
        DO.                     ;Here to free buffers on IO list
         HRRZ A,MSBUFP(W)       ;Get buffer pointer from head of chain
         LDB T,[MLO,,MEMBLT(A)] ;Get back pointer (next buffer)
         HRRM T,MSBUFP(W)       ;Make next buffer head of chain
         PUSHJ P,IMEMR          ;Free current buffer
         SOSLE MSNBOL(W)        ;Decrement count, check for more
         JRST TOP.              ;More, loop back
        ENDDO.
        SETZM MSBUFP(W)         ;Mark list as empty
        JRST POPQJ              ;Restore Q and return

IFN TM10B,[
;Wait for control word to get written
;
MGWCWC: SKIPE MICWA+1           ;Control word written?
         POPJ Q,                ;Yes, return to caller
        CONO MTS,4              ;No, tell DF10 to write it
MGWCW1: SKIPE MICWA+1           ;Written yet?
         JRST MGWCW2            ;Good, done
        PUSHJ Q,CPOPJ           ;Not written. Dismiss interrupt and wait
        JRST MGWCW1             ;We're back. See if written yet.

MGWCW2: MOVE I,MGCMTC(W)
        MOVE J,MGCMTS(W)        ;Restore status
        TLO J,10                ;Set control word written
        POPJ Q,                 ;Return to caller
];IFN TM10B

IFN TM10A,[
MGDCSI: SKIPA A,[BLKI MTC,MIOWD]
MGDCSO:  MOVE A,[BLKO MTC,MIOWD]
        MOVEM A,MAGLOC
        MOVE A,[JSR MGDBRK]
        MOVEM A,MAGLOC+1
        POPJ Q,
];IFN TM10A

IFN TM03S,[
;Note this one's called on P PDL
TMINIC: IORDI A,%TMTC           ;Get TC reg value
        ANDI A,MTSELM           ;Keep interesting bits only
        IORDI B,%TMCS2          ;Get CS2
        ANDI B,7                ;Keep selected "drive" (TM03) number only
        MOVEI T,%TM2CC
        IOWRI T,%TMCS2          ;Clear controller logic
        IOWRI B,%TMCS2          ;Reselect TM03
        IOWRI A,%TMTC           ;Reselect transport
        MOVX T,%TMCLR           ;Do a formatter clear command
        IOWRI T,%TMCS1
        POPJ P,
];IFN TM03S

\f
SUBTTL MAG TAPE PI LEVEL WRITE

MGWRIT: PUSHJ Q,MGGXPT          ;Select desired transport
IFN TM10P,[
        TXNE J,%T1STH\%T1SRW\%T1SWL     ;Write locked, hung or rewinding?
         JRST MGERR             ;Not a good thing
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line?
          JRST MGERR            ;No or no, can't do operation
        TTNE FS,%TMSWL          ;Transport write locked?
         JRST MGERR             ;Shouldn't happen, we checked at open.
]
        MOVSI A,%MACTH
        TDNE A,MSRAC(W)         ;Core alloc want quit temporarly?
         JRST [ PUSHJ Q,CPOPJ   ;OK, wait a while
                JRST MGWRIT ]   ;Then go back and try again
        MOVEM W,MGUNIT          ;Set unit
        HRREI B,-MGNRTY         ;Number of retries
        MOVEM B,MGERRC(W)       ;Store error count
        MTDEQB A                ;Get buffer to write off list
        MOVEM A,MGCABN(W)       ;Note this buffer active at PI
        LDB B,[MWC,,MEMBLT(A)]  ;Get word count from buffer
        MOVNS B                 ;B -> -COUNT
        HRLZS B                 ;B -> -COUNT,,0
IFN KL10P,LSH B,4               ;Shift if KL10 data channel
IFN KL10P,MOVE R,A              ;Save core page number for cache sweep
IFE TM03S,[                     ;TM03S IOWD is -COUNT,,ITS PAGE
        LSH A,10.               ;Convert buffer number to memory address
        SUBI A,1                ;Address - 1
]
        HRRM A,B                ;B -> -COUNT,,ADDRESS-1; an IO word
IFN TM10B,DATAO MTS,[MICWA]     ;Tell DF10 where IO channel program is
IFN TM10A,PUSHJ Q,MGDCSO        ;
        MOVEM B,MIOWD           ;Put IO word where controller looks
        MOVEM B,LMIOWD          ;Remember what we're about to do
IFN TM10P,SETZM MIOWD+1         ;Stop after one operation
IFN KL10P,[
        PUSHJ P,CSHSWP          ;Unload buffer from cache into core
          CAI
]
MGWRT2:
IFN TM10P,[
        MOVE B,MTCONO(W)        ;Get prototype CONO word
        CONO MTC,MWRITE(B)      ;Perform WRITE operation
]
IFN TM03S,[
        HLRE A,MIOWD            ;Get PDP10 word count
        ASH A,1                 ; * 2
        IOWRI A,%TMWC           ; = number of unibus words to transfer
        HLRE A,MIOWD            ;Get PDP10 word count again
        IMUL A,MTWTFC(W)        ;Convert to tape frame count
        IOWRI A,%TMFC           ;Set tape frames to write
        HRRZ A,MIOWD            ;Get ITS page to transfer to
        LSH A,1                 ;Convert ITS pg # to DEC pg #
        TXO A,%UQVAL            ;Valid mapping, I should hope
        IOWRI A,UBAPAG+IUTPG_1  ;Set up first half of UBA mapping
        TXO A,1                 ;Next DEC page number
        IOWRI A,UBAPAG+IUTPG_1+1        ;Set second half of UBA mapping
        MOVEI A,IUTPG_14                ;Unibus address to DMA to
        IOWRI A,%TMBA           ;Tell controller
        MOVX A,%TM1IE\%TMWRT    ;Write, enable interrupts
        IOWRI A,%TMCS1          ;Start controller
]
        PUSHJ Q,MGWTJD          ;Wait for job done
         JRST MGWERR            ;Error, go attempt to repair

;Here if tape written OK
MGWRT3: MOVE A,MGCABN(W)        ;Get buffer number
        HRLZI B,%MAETW+%MAERR   ;End of tape check
IFN TM10P,TXNE J,%T1SET         ;Controller says we're at EOT?
IFN TM03S,TTNE FS,%TMSET
         IORM B,MSRAC(W)        ;Tell MP
        LDB T,[MUR,,MEMBLT(A)]  ;Get buffer flavor from buffer
        CAIE T,MUMGB            ;Still a magtape buffer?
         BUG HALT,[MT BUF CHANGED INTO SOME OTHER KIND??]
        SETOM MGCABN(W)         ;No buffer active at PI anymore
        PUSHJ P,IMEMR           ;Return buffer to system
        MOVSI A,%MAMSO          ;Note tape has moved since open
        IORM A,MSRAC(W)
        ;JRST MGCMDR ;Falls through

;General exit routine for most PI-level command handlers
; Check command queue for more commands.
;  If no further commands, dismiss interrupt.
;  If further commands queued, wait for this one to finish, then fetch
;   and begin processing of next command.
;
MGCMDR: SOS MSCMDC(W)           ;Decrement command count
        SETOM MGUNIT            ;Reset active unit
        SKIPG MSCMDC(W)         ;Any more commands?
         JRST MGCMR1            ;No. Go see about other units
IFN TM10P,[
        MOVE B,MTCONO(W)
        CONO MTC,MNOPIN(B)      ;Tell controller to interupt when unit ready
        MOVEM W,MGUNIT          ;Set up unit number again for MGWTJD
        PUSHJ Q,MGWTJD          ;Go wait for unit to finish current command
         JRST MGERR             ;Oops
        SETOM MGUNIT            ;No unit waiting any more
];IFN TM10P
        POPJ Q,                 ;Return on Q PDL. Most likely this will
                                ; transfer control to MGNCMD routine at
                                ; base of PDL, which will fetch and execute
                                ; next command.

MGCMR1:
IFN NMTCS-1,[
;Ought to check other transports for commands to start.
; For now, will get started by 1/2 second timeout, if nothing else.
        .ERR Unfinished multi-transport code at MGCMR1
];IFN NMTCS-1   
        POPJ P,                 ;No more, return on P to dismiss interrupt


\f
;CONTROLLER DETECTED ERROR ON WRITE OPERATION
; Retry, or give up, or write some blank tape and then try again, 
; depending on the type of error.
;
MGWERR:
IFN TM10P,[
IFN TM10B,SETZM MIOWD           ;Seems to do one record anyway
IFN TM10A,[     
        MOVE A,[-1,,MGVTC-1]
        MOVEM A,MIOWD           ;Specify one record to space back cmd.
]
        TXNE J,%T1STH\%T1SRW\%T1SIO\%T1SET\%T1SWL       ;Bad types of errors
         JRST MGERR             ;OK, give up
        AOSL MGERRC(W)          ;Still retrying?
         JRST MGERR             ;No, give up
        MOVE B,MTCONO(W)
        CONO MTC,MSPRR(B)       ;Space reverse one record
        PUSHJ Q,MGWTJD          ;Wait for job done
         JRST MGERR             ;Error
        MOVE B,LMIOWD           ;Get last operation's IOWD
        MOVEM B,MIOWD           ;We're going to try it again
        MOVE B,MTCONO(W)        ;Get prototype CONO
        CONO MTC,14000(B)       ;Write with extended EOR gap
        PUSHJ Q,MGWTJD          ;Wait for completion
         JRST MGWBT             ;Lost again, retry some more
        JRST MGWRT3             ;Worked, return to normal write sequence
];IFN TM10P
IFN TM03S,[
        TTNE ERR,%TMERM\%TMEUS\%TMEFS\%TMEIR\%TMEIF\%TMEMC\%TMECT\%TMENX\%TMEOI
         JRST MGERR             ;Fatal errors
        TTNN FS,%TMSOL          ;On line?
         JRST MGERR             ;This isn't so good either
        TTNE ERR,%TMEFC\%TMENG\%TMEMD\%TMEIC\%TMECE\%TMECS\%TMEFL
         JRST MGWER1            ;Error which retrying might fix

;Formatter seems happy. Check channel status before returning
; Currently this only catches the case where there was an RH11 error
; but no TM03 error, and thus should always end up jumping to MGERR.
; Formatter errors on which it might be OK to get here are %TMECE,
; %TMECS, %TMEFL, but someone needs to test this...
        TTNE CS1,%TM1TE         ;Transfer error?
         TTNE FS,%TMSES         ;And not formatter error?
          CAIA
           JRST MGERR           ;Just lose for now
        BUG INFO,[MT: ACCEPTING QUESTIONABLE WRITE OPERATION]
        JRST MGWRT3

;Retry errors
MGWER1: AOSL MGERRC(W)          ;Still retrying?
         JRST MGERR             ;No, give up
        BUG INFO,[MT: RETRYING WRITE OPERATION]
        PUSHJ P,TMINIC          ;Hit controller with hammer
        MOVEI B,1
        MOVEM B,MGSPCD(W)       ;1 record
        PUSHJ Q,MGSPCR          ;Reselect transport space back a record
        TTNE FS,%TMSTM          ;Stopped on EOF?
         SOSGE MGEOFR(W)        ;Yes, one less EOF in front of us
          SETZM MGEOFR(W)       ;But never less than zero
        PUSHJ P,TMINIC          ;Hit controller with hammer again
        PUSHJ Q,MGGXPT          ;Set up transport again
        MOVEI B,%TMER3\%TM1IE
        IOWRI B,%TMCS1          ;Erase a few inches of tape
        PUSHJ Q,MGWTJD          ;Wait for job done
         JRST MGERR             ;Can't get anything right...
        MOVE B,LMIOWD           ;Get last operation's IOWD
        MOVEM B,MIOWD           ;We're going to try it again
        JRST MGWRT2             ;Go back to write code and retry operation
];IFN TM03S

\f
SUBTTL MAG TAPE PI LEVEL READ

MGREAD: PUSHJ Q,MGGXPT          ;Select desired transport
MGRD0:  
IFN TM10P,[
        TXNE J,%T1STH\%T1SRW\%T1SET     ;Unit hung, rewinding, or EOT
         JRST MGERR             ;Seems so, report error
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
]
        MOVE B,MGEOFR(W)        ;EOF's seen since last read
        CAIL B,2                ;Apparent logical EOT?
         JRST MGERR             ;Yes, can't read anything
        SKIPE MSCRW(W)          ;Make sure open for reading
         BUG HALT,[MT: CHN NOT OPEN FOR READING]
        MOVSI B,%MACTH          ;Core allocator wants to wait?
        TDNN B,MSRAC(W)         ;Check in status word
         PUSHJ P,IOMQ           ;No, get a buffer
          JRST [PUSHJ Q,CPOPJ   ;Wanted to wait some or failed,
                JRST MGREAD ]   ; wait a while, then start over
        MOVEM A,MGCABN(W)       ;Note active buffer at PI level
        MOVEI B,MUMGB
        DPB B,[MUR,,MEMBLT(A)]  ;Note buffer belongs to mag tape code
        MOVEM W,MGUNIT          ;Set active unit number
        HRREI B,-MGNRTY         ;Number of retries
        MOVEM B,MGERRC(W)       ;Store error count
IFN KL10P, MOVE R,A             ;Get page for cache flush routine
IFE TM03S,[                     ;TM03S IOWD is -COUNT,,ITS PAGE
        LSH A,10.               ;Convert buffer number to memory address
        SUBI A,1                ;address-1
]
IFE KL10P,HRLI B,-2000          ;Get count half of IOWD
IFN KL10P,HRLI B,-2000_4        ;The KL is, of course, different
        HRR B,A                 ;-count,,address-1
        MOVEM B,LMIOWD          ;Remember IOWD for possible retry
IFN TM10B,[
        DATAO MTS,[MICWA]       ;Tell DF10 where the channel program is
        SETZM MICWA+1           ;Stop after one operation
]
IFN TM10A,PUSHJ Q,MGDCSI
IFN TM10P,SETZM MIOWD+1
MGRD1:  MOVEM B,MIOWD           ;Save IOWD where channel expects it
        MOVEI B,2000            ;Assume for now that the record has 2K words
        MOVEM B,MGNWRD          ;Set up word count
IFN KL10P,[
        PUSHJ P,CSHSWP          ;Ensure no residue of this page in cache
            CAIA
]
IFN KS10P,CLRCSH                ;KS needs cache invalidated on read
IFN TM10P,[
        MOVE B,MTCONO(W)        ;Get prototype CONO word
        CONO MTC,MREAD(B)       ;Issue READ command
]
IFN TM03S,[
        HLRE A,MIOWD            ;Get PDP10 word count
        ASH A,1                 ; * 2
        IOWRI A,%TMWC           ; = number of unibus words to transfer
        SETZ A,                 ;Set FC to zero
        IOWRI A,%TMFC           ;Set tape frames to write
        HRRZ A,MIOWD            ;Get ITS page to transfer to
        LSH A,1                 ;Convert ITS pg # to DEC pg #
        TXO A,%UQVAL
        IOWRI A,UBAPAG+IUTPG_1  ;Set up first half of UBA mapping
        TXO A,1                 ;Next DEC page number
        IOWRI A,UBAPAG+IUTPG_1+1        ;Set second half of UBA mapping
        MOVEI A,IUTPG_14        ;Unibus address for DMA
        IOWRI A,%TMBA           ;Tell controller
        MOVX A,%TM1IE\%TMRDF    ;Read forward, enable interrupts
        IOWRI A,%TMCS1          ;Start controller
];IFN TM03S
IFN TM10B,SETOM MGWCW           ;Tell MGWTJD to wait for control word written
        PUSHJ Q,MGWTJD          ;Wait for command to complete
         JRST MGRERR            ;Error, go do something. May be retry, correct
                                ; MGNWRD if frame count error, or give up
IFN TM03S,[
;Get true record size for TM03, which doesn't give a FC error on READ
MGRD1A: TTNE FS,%TMSTM          ;Read a tape mark?
         JRST [ SETZM MGNWRD    ;Read a tape mark. No data, just EOF
                JRST MGRD2 ]
        IORDI A,%TMFC           ;Get record size in tape frames
        ADD A,MTWTFC(W)         ;Round up to PDP10 words.
        SUBI A,1                ;Add frames_per_word - 1
        IDIV A,MTWTFC(W)        ;Get record size in PDP10 words
        MOVEM A,MGNWRD
];IFN TM03S
;Here if OK or error handler has fixed things up
MGRD2:  MOVE A,MGCABN(W)        ;Get buffer we just wrote
        SETOM MGCABN(W)         ;No buffer active at PI level
        MTENQB A                ;Queue buffer up for MP level
        MOVE B,MGNWRD           ;Get number of words we read
        DPB B,[MWC,,MEMBLT(A)]  ;Set number of words in buffer
IFN TM10P,TXNE J,%T1SEF         ;Read an EOF?
IFN TM03S,TTNE FS,%TMSTM        ; i.e. a tape mark?
        IFSKP.
         SETZM MGEOFR(W)        ;No. Note no EOFs read since last record
        ELSE.
         MOVSI B,%MAESO+%MAEFA  ;EOF seen since open, EOF read ahead
         IORM B,MSRAC(W)        ;Note this in transport status word
         SETO B,
         DPB B,[MSEOFP,,MEMBLT(A)]      ;Set EOF flag in this buffer
         AOS A,MGEOFR(W)        ;Count EOFs
         CAIL A,2               ;Enough for EOT?
          JRST MGRD4            ;Logical EOT, space back over it
        ENDIF.
        MOVSI A,%MAMSO
        IORB A,MSRAC(W)         ;Note tape movement
IFN TM10P,TXNE J,%T1SET         ;Real EOT reached?
IFN TM03S,TTNE FS,%TMSET
         JRST MGRD3
        MOVE C,MSNBOL(W)        ;Get count of buffers on list
IFN TM10P,TXNN J,%T1SEF         ;EOF?
IFN TM03S,TTNN FS,%TMSTM

;        CAIL C,6               ; or read ahead six records?
        JFCL                    ;Or just for the hell of it

          JRST MGRD5            ;Yes, stop reading
        TLNN A,%MASTP           ;Somebody request we stop?
         JRST MGRD0             ;No, go back and read another record
                                ;Yes, fall through to terminate read
;Here to terminate read command
;
MGRD5:  MOVSI A,%MASTP+%MARAC   ;Clear read active, any read stop request
        ANDCAM A,MSRAC(W)
        JRST MGCMDR             ;Go to standard command return routine

;Controller saw a real EOT
;
MGRD3:  DPB B,[MSEOFP,,MEMBLT(A)]       ;Fake EOF
        DPB B,[420100,,MSRAC(W)] .SEE %MAETR    ;Indicate EOT on read
        JRST MGRD5              ;Terminate read

;Here if logical EOT (two EOF's in a row)
; Back up till between the two EOF's
;
MGRD4:  MOVSI A,%MAESO+%MARAC+%MASTP    ;SECOND EOF, LOGICAL EOT
        ANDCAM A,MSRAC(W)
        JRST MGSPRF             ;Space reverse one file

;Error detected on read.
; Analyze error, retry read if it might help
;
MGRERR:
IFN TM10P,[
 IFN TM10B,[
        TXNE J,%T1SCP\%T1SNM\%T1SDP
         JRST MGERR             ;Channel error, forget it
 ]
        TXNE J,%T1STH\%T1SRW\%T1SIO\%T1SRC      ;Hard error?
         JRST MGERR             ;Yes, abandon read
        TXNE J,%T1SPE\%T1SDL%T1SBT      ;Parity, data-late, or bad tape?
         JRST MGMRT             ;Yes, a read retry might fix it
        TXNN J,%T1SRL           ;Record length error?
         JRST MGERR             ;No, who knows what is going on

;Here if record length error. Adjust MGNWRD to reflect data actually read
;
IFN TM10B,HRRZ A,MICWA+1
IFN TM10A,HRRZ A,MIOWD          ;Get final control word
        HRRZ B,LMIOWD           ;Get original IOWD
        SUB A,B                 ;Calculate words read
IFN TM10B,SOS A                 ;Channel funnyness
        CAIE A,1                ;Length of 1 may just be EOF indication
        IFSKP.
         TXNE J,%T1SEF\%T1SET   ;1 word, EOF? EOT?
          SETZM A               ;Yes, zero length record, just carries MSEOFP
        ENDIF.
        MOVEM A,MGNWRD          ;Save new record length
        JRST MGRD2              ;Go process as potentially correctly read data
];IFN TM10P
IFN TM03S,[
        TTNE ERR,%TMERM\%TMEUS\%TMEFS\%TMEIR\%TMEIF\%TMEMC\%TMECT\%TMENX
         JRST MGERR             ;Fatal errors
        TTNN FS,%TMSOL          ;On line?
         JRST MGERR             ;This isn't so good either
        TTZ ERR,%TMEFC\%TMENG   ;Ignore NSG, Frame count error
        TTNE FS,%TMSPE          ;Phase encoded (1600BPI) mode?
         TTZ ERR,%TMECE\%TMECS  ;If so, ignore errors hardware already fixed
        TTZN ERR,%TMECE\%TMECS\%TMEFC\%TMENG\%TMEFL\%TMEMD\%TMEIC ;Retryable?
         JRST MGRER1            ;Nothing retrying will help
        TTNE FS,%TMSTM          ;Tape mark?
         JRST MGRER2            ;Yes, no point in retrying
        JRST MGMRT              ;OK, go retry read

;Formatter seems happy. Check channel status before returning
MGRER1: TTNE ERR,177777         ;Sanity check. Shouldn't be any errors left
         JRST MGERR
        TTNE CS1,%TM1TE         ;Transfer error?
         TTNE FS,%TMSES         ;And not formatter error?
          CAIA
           JRST MGERR           ;Just lose for now
MGRER2: JRST MGRD1A

];IFN TM03S

\f
;Retry a read operation
;
MGMRT:  AOSL MGERRC(W)          ;Still retrying?
         JRST MGERR             ;No, give up
IFN TM10P,[
 IFN TM10B,SETZM MIOWD
 IFN TM10A,[
        MOVE A,[-1,,MGVTC-1]
 ]
        MOVEM A,MIOWD           ;One record
        PUSHJ Q,MGDCSO
        MOVE B,MTCONO(W)
        CONO MTC,MSPRR(B)       ;Back up one record
        PUSHJ Q,MGWTJD          ;Wait till done
         JRST MGERR             ;No errors allowed
 IFN TM10A,PUSHJ Q,MGDCSI       ;Put back PI 1 BLKI
];IFN TM10P
IFN TM03S,[
        IORDI T,%TMFS           ;Get current formatter status
        TXNN T,%TMSES           ;Showing error?
        IFSKP.                  ;Have to clear it before backing up
         MOVEI A,10.            ;Try 10 times to clear drive
         MOVEI B,%TMCLR
         DO.
          IOWRI B,%TMCS1        ;Write drive clear command
          IORDI T,%TMFS         ;Get status
          TXNN T,%TMSES         ;Still have error
           JRST ENDLP.          ;No, done
          SOJG A,TOP.           ;Retry up to 10 times
          JRST MGERR            ;Else give up
         ENDDO.
        ENDIF.
        MOVE T,MTSELW(W)        ;Get desired settings
        IOWRI T,%TMTC           ;Tell TM03
        SETO A,
        IOWRI A,%TMFC           ;1 record
        MOVEI A,%TM1IE\%TMSPR   ;Space backwards command
        IOWRI A,%TMCS1          ;Do it
        PUSHJ Q,MGWTJD          ;Wait till finished
         JRST MGERR             ;Give up if error
];IFN TM03S
        MOVE B,LMIOWD           ;Get IOWD from last command
        JRST MGRD1              ;Try operation again

\f
SUBTTL MAG TAPE PI LEVEL SPACING COMMANDS
;Space forward and space reverse are completely under conditionals

IFN TM03S,[

;Space forward MGSPCD(W) records
MGSPCF: PUSHJ Q,MGGXPT          ;Acquire transport
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
        MOVEM W,MGUNIT          ;Note active transport
        MOVN A,MGSPCD(W)        ;Get -count
        IOWRI A,%TMFC           ;Tell controller
        MOVEI A,%TMSPF          ;Get command
        TXO A,%TM1IE            ;Turn on interrupts
        IOWRI A,%TMCS1          ;Start controller
        PUSHJ Q,MGWTJD          ;Wait till command completes
        IFNSK.                  ;Error?
         TTNE CS1,%TM1MP        ;Control parity err?
          JRST MGERR            ;Yes, nothing else valid
         TTNE FS,%TMSES         ;Formatter errors?
         IFSKP.
          PUSHJ P, TMINIC       ;No formatter errors, ignore RH errors
         ELSE.
          TTNN ERR,%TMEFC       ;Frame count error?
           JRST MGERR           ;Nope, must be important
          PUSHJ P,TMINIC
         ENDIF.
        ENDIF.
        POPJ Q,

;Space forward record
MGSPFR: MOVEI B,1               ;Do one record
        MOVEM B,MGSPCD(W)       ;Set count
        MOVSI B,%MAMSO          ;Note this command causes tape movement
        IORM B,MSRAC(W)         ;Set in transport software status
        PUSHJ Q,MGSPCF          ;Do spacing op
        TTNN FS,%TMSTM
         SETZB B,MGEOFR(W)      ;Count EOFs since last record. None here
        TTNE FS,%TMSTM
         AOS B,MGEOFR(W)        ;Saw one.
        CAIL B,2                ;Saw two?
         JRST MGSPRR            ;Back up over last one...
        JRST MGCMDR             ;Clean up and leave

;Space forward file
MGSPFF: MOVSI B,%MAESO          ;See if tape has already read ahead to EOF
        TDZE B,MSRAC(W)
         JRST MGCMDR            ;EOF already read during the read, done
        MOVEI B,1               ;Do one record
        MOVEM B,MGSPCD(W)       ;Set count
        MOVSI B,%MAMSO          ;Note this command causes tape movement
        IORM B,MSRAC(W)         ;Set in transport software status
        PUSHJ Q,MGSPCF          ;Space forward one record
        TTNN FS,%TMSTM
        IFSKP.                  ;Saw a TM
         AOS B,MGEOFR(W)        ;Saw one.
         CAIL B,2               ;Saw two?
          JRST MGSPRR           ;Yes, back up over last one, and leave
         JRST MGCMDR            ;No, OK, but we're done
        ENDIF.
        SETZB B,MGEOFR(W)       ;No tape mark, reset count of EOFs seen
MGSPF1: MOVEM B,MGSPCD(W)       ;Set count to 0 (B zero from above)
        PUSHJ Q,MGSPCF          ;Do it
        TTNE FS,%TMSTM          ;Saw a EOF?
        IFSKP.                  ;No..
         TTNE FS,%TMSET         ;Saw an EOT?
          JRST MGERR            ;Really shouldn't happen
         JRST MGSPF1            ;Else go look for TM again
        ENDIF.
        AOS MGEOFR(W)           ;Saw one.
        JRST MGCMDR             ;EOF read. done

;Space reverse MGSPCD(W) records
MGSPCR: PUSHJ Q,MGGXPT          ;Set up transport and get status
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
        TTNE FS,%TMSBT          ;At BOT?
         POPJ Q,
        MOVEM W,MGUNIT          ;Save selected transport
        MOVN A,MGSPCD(W)        ;Get -count
        IOWRI A,%TMFC           ;Tell controller
        MOVEI A,%TMSPR          ;Space Reverse command
        TXO A,%TM1IE            ;Turn on interrupts
        IOWRI A,%TMCS1          ;Start controller
        PUSHJ Q,MGWTJD          ;Wait till command completes
        IFNSK.                  ;Error?
         TTNE CS1,%TM1MP        ;Control parity err?
          JRST MGERR            ;Yes, nothing else valid
         TTNE FS,%TMSES
         IFSKP.
          PUSHJ P,TMINIC
         ELSE.
          TTNN ERR,%TMEFC       ;Frame count error?
           JRST MGERR           ;Nope, must be important
          PUSHJ P,TMINIC
         ENDIF.
        ENDIF.
        POPJ Q,

;Space reverse one record
MGSPRR: MOVEI B,1
        MOVEM B,MGSPCD(W)       ;1 record
        MOVSI B,%MAMSO          ;Note this command causes tape movement
        IORM B,MSRAC(W)         ;Set in transport software status
        PUSHJ Q,MGSPCR
        TTNE FS,%TMSTM          ;Stopped on EOF?
         SOSGE MGEOFR(W)        ;Yes, one less EOF in front of us
          SETZM MGEOFR(W)       ;But never less than zero
        JRST MGCMDR             ;Leave through general exit     

;Space reverse fill
MGSPRF: MOVSI B,%MAESO          ;See if tape has already read ahead to EOF
        TDNN B,MSRAC(W)
         JRST MGSPR2            ;No, we can just do command
MGSPR1: MOVEI B,1
        MOVEM B,MGSPCD(W)
        PUSHJ Q,MGSPCR          ;Skip back 1 record, should backup over EOF
        TTNN FS,%TMSTM          ;Tape mark seen?
         JRST MGSPR1            ;Well, apparently not
        MOVSI B,%MAESO
        ANDCAM B,MSRAC(W)       ;Turn off EOF-read-ahead flag
MGSPR2: SETZ B,
        MOVEM B,MGSPCD(W)       ;Space backwards the maximum number of records
        PUSHJ Q,MGSPCR          ;Do it
        TTNN FS,%TMSBT          ;BOT?
         TTNE FS,%TMSTM         ;Tape mark seen?
          JRST MGCMDR           ;Yes or Yes, all done
        JRST MGSPR2             ;No, go back and try to find one.

];End TM03S way back

\f;Rewind commands
;
MGRWND:
IFN TM10P,MOVEI B,MREWND        ;Normal rewind
IFN TM03S,MOVEI B,%TMREW
        CAIA
MGRWDM:
IFN TM10P, MOVEI B,MRWNDD       ;Rewind and dismount
IFN TM03S, MOVEI B,%TMUNL
        MOVEM B,MGSPCD(W)       ;Set up command
        PUSHJ Q,MGRWD1          ;Call action routine
        JRST MGCMDR

;Action routine for rewind commands
MGRWD1: PUSHJ Q,MGGXPT
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
]
        MOVEM W,MGUNIT
        MOVE B,MGSPCD(W)        ;Get desired command
IFN TM10P,[
        ADD B,MTCONO(W)
        CONO MTC,(B)
]
IFN TM03S,[
        TXO B,%TM1IE
        IOWRI B,%TMCS1
]
        PUSHJ Q,MGWTJD          ;Start controller and wait till done
        IFNSK.
         TTNE FS,%TMSES
          JRST MGERR            ;Oops.
        ENDIF.
        SETZM MGEOFR(W)         ;Seen no EOFs since last record

;Here after rewind command has started.
;  Two possibilities: Tape is rewound already, or controller is finished
;  but tape is still rewinding.
IFN TM10P,[
MGRWD2: TXNN J,%T1SRW           ;Slave still rewinding tape?
         JRST MGRWD3            ;No, at BOT
        PUSHJ Q,CPOPJ           ;Wait some.
        CONI MTS,J              ;Get status again
        MOVEM J,MGCMTS(W)       ;Update in memory
        JRST MGRWD2             ;Go see if we're done yet.

;Here when tape has rewound
MGRWD3: MOVE T,TIME             ;Wait 1 second more
        ADDI T,30.              ;This is an attempt to fix a hardware bug
        MOVEM T,MGJDTI
MGRWD4: MOVE T,TIME
        CAML T,MGJDTI           ;Check time
         JRST MGRWD5            ;Finished waiting, go clean up
        PUSHJ Q,CPOPJ           ;No, wait some more
        JRST MGRWD4

MGRWD5: MOVSI A,%MAMSO+%MAREW
        ANDCAM A,MSRAC(W)       ;Say not rewinding, hasn't moved
        SETZM MGJDTI            ;Clear timeout
        POPJ Q,
];IFN TM10P
IFN TM03S,[
;This could be a lot smarter; should dismiss the command completely
; after rewind is started, and just scan for rewinding transports
; when a SSC interrupt is received. This change is also necessary
; to make multiple slaves work right; currently the rewinding unit
; holds active unit (MGUNIT) until the rewind is completed.
MGRWD2: TTNN FS,%TMSPP          ;Transport still rewinding?
         JRST MGRWD3            ;No, go finish up
        PUSHJ Q,CPOPJ           ;Dismiss interrupt, wait a while
        PUSHJ Q,MGGXPT          ;Get right slave, set up status
        JRST MGRWD2

MGRWD3: MOVSI A,%MAMSO+%MAREW
        ANDCAM A,MSRAC(W)       ;Say not rewinding, hasn't moved
        POPJ Q,
];IFN TM03S
\f
;SKIP TO LOGICAL EOT
;
MGSEOT: PUSHJ Q,MGGXPT          ;Get transport
IFN TM10P,[
        TXNE J,%T1STH\%T1SRW    ;Hung or rewinding?
         JRST MGERR
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
]
        MOVEM W,MGUNIT          ;Set active unit
IFN TM10P,TXNE J,%T1SBT         ;BOT?
IFN TM03S,TTNE FS,%TMSBT
         JRST MGVTCK            ;Yep, do virgin tape check

;Not at BOT
; Do we have enough CONDITIONALS yet?
MGNVT:  
IFN TM10P,[
        MOVE B,MTCONO(W)        ;Get CONO word
 IFN TM10A,[
        PUSHJ Q,MGDCSO
        MOVE A,[-1,,MGVTC-1]
        MOVEM A,MIOWD           ;Tell it to move one record
 ]
 IFN TM10B,SETZM MIOWD
        CONO MTC,MSPRR(B)       ;Space reverse first
];IFN TM10P
IFN TM03S,[
        SETO B,                 ;Space backwards one record
        IOWRI B,%TMFC
        MOVEI B,%TMSPR\%TM1IE
        IOWRI B,%TMCS1
];IFN TM03S
        PUSHJ Q,MGWTJD          ;Wait till done
        IFNSK.
         TTNE FS,%TMSES
          JRST MGERR
        ENDIF.
        SETZM MGEOFR(W)
        AOS MGEOFR(W)           ;Claim to have seen one EOF
MGEOT2: 
IFN TM10P,[
        MOVE B,MTCONO(W)
        CONO MTC,MSPFF(B)       ;Skip forward to EOF
        PUSHJ Q,MGWTJD
         JRST MGERR
]
IFN TM03S,[
        AOS MSCMDC(W)           ;Kludge so MGSPFF will return here.
        PUSHJ Q,MGSPFF          ;Space forward file
]
        MOVSI B,%MAETR          ;See if we hit real EOT
IFN TM10P, TXNE J,%T1SET
IFN TM03S, TTNE FS,%TMSET
         IORM B,MSRAC(W)        ;Yep, tell MP
IFN TM10P,[
        MOVE B,MTCONO(W)
 IFN TM10A,[
        MOVE A,[-1,,MGVTC-1]
        MOVEM A,MIOWD           ;One record
 ]
 IFN TM10B,SETZM MIOWD
        CONO MTC,MSPFR(B)       ;Space forward one record
]
IFN TM03S,[
        SETO B,
        IOWRI B,%TMFC
        MOVEI B,%TMSPF\%TM1IE
        IOWRI B,%TMCS1
]
        PUSHJ Q,MGWTJD
        IFNSK.
         TTNE FS,%TMSES
         JRST MGERR
        ENDIF.
        MOVSI B,%MAETR          ;Check for real EOT again
IFN TM10P,TXNE J,%T1SET
IFN TM03S,TTNE FS,%TMSET
         IORM B,MSRAC(W)
IFN TM10P,TXNN J,%T1SEF         ;Is this another EOF?
IFN TM03S,TTNN FS,%TMSTM        ;(i.e. a tape mark)
         JRST MGEOT2            ;No, not at logical EOT. Go try again
IFN TM10P,[
        MOVE B,MTCONO(W)        ;Yes, at logical EOT, Back up over 1 EOF
        CONO MTC,MSPRF(B)       ;Space back one file
]
IFN TM03S,[
        SETO B,
        IOWRI B,%TMFC
        MOVEI B,%TMSPR\%TM1IE
        IOWRI B,%TMCS1
]
        PUSHJ Q,MGWTJD
        IFNSK.
         TTNE FS,%TMSES
         JRST MGERR
        ENDIF.
        MOVSI B,%MAEOF+%MAETR   ;Tell MP at EOF, EOT
        IORM B,MSRAC(W)
        JRST MGCMDR
\f
;Check for virgin tape
MGVTCK: MOVE T,TIME
        ADDI T,60.              ;Set a two second timeout
        MOVEM T,MGEOTT(W)       ; before we must see an EOT
IFN TM10P,[
 IFN TM10B,[
        SETZM MIOWD
        DATAO MTS,[MICWA]
 ]
 IFN TM10A,[
        MOVE A,[-1,,MGVTC-1]
        MOVEM A,MIOWD
        PUSHJ Q,MGDCSO
 ]
        MOVE B,MTCONO(W)
        CONO MTC,MREAD(B)       ;Read record. will time out if no EOF marks
MGVTC1: CONI MTS,J
        MOVEM J,MGCMTS(W)
        TXNE J,%T1SJD           ;Job done?
         JRST MGNVT             ;Yep,  not virgin tape
        TXNE J,%T1STH\%T1SIO    ;Transport hung or illegal operation?
         JRST MGERR             ;Yes, give up
        MOVE T,MGEOTT(W)        ;Get the timeout value
        CAMG T,TIME             ;Time up?
         JRST MGVT              ;Yes, it's a new tape
        PUSHJ Q,CPOPJ           ;Wait a while
        JRST MGVTC1             ;Go back and check again
];IFN TM10P
IFN TM03S,[
        SETO B,
        IOWRI B,%TMFC           ;Do one record
        MOVEI B,%TMSPF\%TM1IE   ;Space forward command
        IOWRI B,%TMCS1

MGVTC1: IORDI T,%TMCS1          ;Get status
        TXNN T,%TM1GO           ;Still going?
        IFSKP.                  ;Yep.
         MOVE T,MGEOTT(W)       ;Get the timeout value
         CAMG T,TIME            ;Time up?
          JRST MGVT             ;Yes, it's a new tape
         PUSHJ Q,CPOPJ          ;Wait a while
         JRST MGVTC1            ;Go back and check again
        ENDIF.
        TXNE T,%TM1TE\%TM1MP    ;Controller error?
         JRST MGERR             ;Yes, bad
        IORDI T,%TMFS           ;Get formatter status
        TXNE T,%TMSES           ;Formatter error?
         JRST MGNVT             ;No error, not a new tape
        IORDI T,%TMERR          ;Get formatter error register
        TXNE T,%TMEFC           ;Frame Count error?
         JRST MGNVT             ;Yes, that is probably an OK tape
        JRST MGERR              ;Not FC, must be a real problem
];IFN TM03S
\f
;Virgin tape. Abort operation in progress, rewind tape
MGVT:   
IFN TM10P,[
        MOVE B,MTCONO(W)
        CONO MTS,31             ;Clear controller
        CONO MTC,MNOPIN(B)      ;Start new command to clear things out
        PUSHJ Q,MGWTJD
         JFCL                   ;Ignore errors
]
IFN TM03S,[
        PUSHJ P,TMINIC
]
IFN TM10P,MOVEI B,MREWND                ;Do a rewind
IFN TM03S,MOVEI B,%TMREW
        MOVEM B,MGSPCD(W)
        PUSHJ Q,MGRWD1  
        SETZM MGEOFR(W)         ;No EOFs seen
        AOS MGEOFR(W)           ;???
        JRST MGCMDR             ;Done

;Write EOT mark (two EOF's) on tape
;
MGMEOT: PUSHJ Q,MGGXPT
IFN TM10P,[
        TXNE J,%T1STH\%T1SRW\%T1SWL ;Hung, rewinding, or write locked...
         JRST MGERR
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
        TTNE FS,%TMSWL          ;Transport write locked?
         JRST MGERR             ;Shouldn't happen, we checked at open.
];IFN TM03S
        MOVEM W,MGUNIT          ;Note active unit
        SKIPE MTCEFW(W)         ;Check # of EOF's already written
        IFSKP.                  ;None. Need to write two
         AOS MSCMDC(W)          ;Kludge so MGWEOF will return here.
         AOS MTCEFW(W)          ;Increment EOF count
         PUSHJ Q,MGWEOF         ;Write an EOF
        ENDIF.
        MOVE A,MTCEFW(W)        ;Get EOF count
        SOSLE A                 ;Check for at least two EOF's written
        IFSKP.                  ;No, need one more on tape
         AOS MSCMDC(W)          ;Again, force MGWEOF to return
         AOS MTCEFW(W)          ;Incr EOF count
         PUSHJ Q,MGWEOF         ;Write EOF
        ENDIF.
        MOVE A,MSRAC(W)         ;Get transport software status
        TLNE A,%MANWT           ;Are we supposed to back up over last EOF?
        IFSKP.
         AOS MSCMDC(W)          ;Yes. Force MGSPRF to return, then...
         PUSHJ Q,MGSPRF         ; ...do space reverse file command
        ENDIF.
        MOVSI A,%MANWT          ;Note what we've done
        IORM A,MSRAC(W)         
        JRST MGCMDR             ;Leave through general exit routine
\f
;Write one EOF mark on tape
;
MGWEOF: PUSHJ Q,MGGXPT          ;Set up transport for IO
IFN TM10P,[     
        TXNE J,%T1STH\%T1SRW\%T1SWL ;Hung, rewinding, or write locked...
         JRST MGERR             ; ..lose
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
        TTNE FS,%TMSWL          ;Transport write locked?
         JRST MGERR             ;Shouldn't happen, we checked at open.
]
        MOVEM W,MGUNIT          ;Remember active unit
IFN TM10P,[
        MOVE B,MTCONO(W)        ;Get CONO word for this unit
        CONO MTC,MWEOF(B)       ;Execute Write EOF function
]
IFN TM03S,[
        MOVEI B,%TM1IE\%TMWTM   ;Write tape mark, enable interrupts
        IOWRI B,%TMCS1          ;Do it
]
        PUSHJ Q,MGWTJD          ;Wait around till command is complete
        IFNSK.
         TTNE FS,%TMSES
         JRST MGERR
        ENDIF.
        MOVSI A,%MAMSO
        IORM A,MSRAC(W)         ;Note tape movement in software status
        JRST MGCMDR             ;Return through general exit routine

;Get transport and controller status
;
MGSTAT: PUSHJ Q,MGGXPT
        JRST MGCMDR

;Write some blank space
;
MGW3IN: PUSHJ Q,MGGXPT
IFN TM10P,[
        TXNE J,%T1STH\%T1SRW\%T1SWL ;Hung, rewinding, or write locked...
         JRST MGERR
]
IFN TM03S,[
        TTNE FS,%TMSFR          ;Formatter ready?
         TTNN FS,%TMSOL         ;Transport on line
          JRST MGERR            ;No or no, can't do operation
        TTNE FS,%TMSWL          ;Transport write locked?
         JRST MGERR             ;Shouldn't happen, we checked at open.
];IFN TM03S
        MOVEM W,MGUNIT          ;Note active transport
IFN TM10P,[                     
;TM10 can't just write blank space, it has to write blank space followed
; by a data record
 IFN TM10B,[
        SETZM MIOWD             ;Tell TM10 to write 1-word record
        DATAO MTS,[MICWA]
 ]
 IFN TM10A,[
        MOVE A,[-1,,MGVTC-1]    ;1-word record
        MOVEM A,MIOWD
        PUSHJ Q,MGDCSO
 ]
        MOVE B,MTCONO(W)
        CONO MTC,MW3IN(B)       ;Write date record preceeded by 3-in gap
];IFN TM10P
IFN TM03S,[
        MOVEI B,%TM1IE\%TMER3   ;Erase 3 inches command, enable interrupts
        IOWRI B,%TMCS1          ;Do it
];IFN TM03S
        PUSHJ Q,MGWTJD          ;Wait...
         JFCL                   ;Ignore errors (really should check kind)
IFN TM10P,JRST MGSPRR           ;Now space record reverse over the bogus record
IFN TM03S,JRST MGCMDR           ;TM03 does it right

\f
SUBTTL .MTAPE UUO 

;.MTAPE AC,
;       AC/     CHNM,COMMAND
;               COMMAND/        COUNT,,FUNCTION

AMTAPE: XCTR XR,[HLRZ R,(J)]    ;Get IO channel from user
        TRNE R,-NIOCHN          ;Legal channel?
         JRST ILUUO             ;Lose
        HRRZM R,UUAC(U)         ;Cause errors to report on the correct channel
        ADDI R,IOCHNM(U)        ;Form IOCHNM pointer
        LDB W,[MTXP(R)]         ;Get transport number
        CAME U,MTUSR(W)         ;Same user?
         POPJ P,                ;No, give up
        XCTR XR,[MOVE J,(J)]    ;Get Channel,,Command from user
        MOVEM J,MTMTAP(W)       ;Save it
        HRRZ A,MTMTAP(W)        ;Get address of Count,,Function word
        PUSHJ P,MTIECK          ;Check transport for error states
        XCTR XR,[MOVE A,(A)]    ;Get count,,function from user
        HRRZM A,MTMFNC(W)       ;Store function
        HLREM A,MTMCNT(W)       ; and count
        SKIPN MTMCNT(W)         ;Count of zero always means one, for
         AOS MTMCNT(W)          ; compatibility with the old code.
        HRRZS A
        CAIL A,NMTAPC           ;Command in range?
         POPJ P,                ;No...
        AOS (P)                 ;Command OK, skip return
        JRST @MTAPDT(A)         ;Go do command

MTAPDT: MTHANG                  ;0 Hang till tape motion done
        MTRWND                  ;1 Rewind
        MTRWDM                  ;2 Rewind and dismount
        MTWEOR                  ;3 Write EOR if appropriate
        MTW3IN                  ;4 Write 3 inches of blank tape
        MTWEOF                  ;5 Write EOF
        MTSPR                   ;6 Space records
        MTSPF                   ;7 Space files
        MTSPEOT                 ;10 Space to EOT
        MTSTOP                  ;11 Abort all operations immediately
        MTSBKS                  ;12 Set block size (to COUNT)
        MTRBKS                  ;13 Read block size (to AC)
IFN 0,[
        MTRTSW                  ;14 Read Transport Information (to AC)
        MTRTEW                  ;15 Read Tape Error Word (to AC)
]
NMTAPC==.-MTAPDT

;Set block size for write
;
MTSBKS: MOVE A,MTMCNT(W)        ;Desired blocksize
        CAIL A,4                ;Check reasonableness
         CAILE A,2000
          SOSA (P)              ;Fail if too big or too small
           MOVEM A,MTBLKS(W)    ;OK, change write-buffer size
        POPJ P,

;Read current write blocksize
;
MTRBKS: MOVE A,MTBLKS(W)        ;Get current write block size
        JRST APTUAJ             ;Return it
\f
;Hang until all motion finished
;
MTHANG: SKIPLE MSCMDC(W)        ;Check count of queued commands
         PUSHJ P,UFLS           ;Wait if there are any
        JRST MTIECK             ;Done, check for errors and return

;Rewind, Rewind and dismount
;
MTRWND: SKIPA B,[MGRWND]        ;Get "REWIND" PI level command
MTRWDM:  MOVEI B,MGRWDM         ; or "REWIND and DISMOUNT" if appropriate
        SKIPE MSCRW(W)          ;Writing?
         JRST MTSOSP            ;Yes, error. Go undo skip rtn and exit
        MOVSI A,%MAREW          ;Note rewinding in software status
        IORM A,MSRAC(W)
        JRST MTCMD              ;Go queue command for PI level


;"Write End of Record" 
; This is really the FORCE system call, or should be.
;
MTWEOR: SKIPG MTMDN(W)          ;MP level have an active buffer?
         POPJ P,                ;No, nothing to do
        SKIPE MSCRW(W)          ;Writing?
         JRST MTWBFD            ;Yes, go write buffer to tape
MTSOSP: SOS (P)                 ;Not writing, error. Undo skip return
        POPJ P,                 ;Return

;Write EOF
;
MTWEOF: SKIPN MSCRW(W)          ;Writing?
         JRST MTSOSP            ;No, can't write EOF. Take error exit
        PUSHJ P,MTWEOR          ;Flush current buffer, if any
        MOVEI B,MGWEOF          ;Get PI level EOF routine
        AOS MTCEFW(W)           ;Increment count of EOF's written
        MOVSI TT,%MANWT         ;Flag something written on tape
        ANDCAM TT,MSRAC(W)
        JRST MTCMD              ;Queue MGWEOF command for PI level

;Write blank tape
;
MTW3IN: SKIPN MSCRW(W)          ;Error if tape not open for write
         JRST MTSOSP
        MOVEI B,MGW3IN          ;Get PI level command
        SETZM MTCEFW(W)         ;No EOF's since last record
        MOVSI TT,%MANWT
        ANDCAM TT,MSRAC(W)      ;Note written something to tape
        JRST MTCMD              ;Go queue command for PI

;Space records, +=forward, -=back
;
MTSPR:  SKIPE MSCRW(W)          ;Not allowed if writing
         JRST MTSOSP
        PUSHJ P,MTFLRA          ;Flush read-ahead, find out how far off we are
        ADD B,C                 ;Get records tape is ahead of user (EOF=record)
        MOVNS B                 ;Subtract this from user's request
        ADDB B,MTMCNT(W)        ;Adjust count
        JUMPE B,CPOPJ           ;If count is now zero, we are done
MTSPR1: PUSHJ P,MTCNTR          ;Update user's copy in case PCLSR
        JUMPG B,MTSPFR          ;Space forward
        MOVEI B,MGSPRR          ;Get SPACE REVERSE command
        PUSHJ P,MTCMD           ;Queue it
        AOSGE B,MTMCNT(W)       ;Increment count, check if done
         JRST MTSPR1            ;More
        POPJ P,                 ;No more

MTSPFR: MOVEI B,MGSPFR          ;Get SPACE FORWARD command
        PUSHJ P,MTCMD           ;Queue it
        SOSLE B,MTMCNT(W)       ;Decr count, check if done
         JRST MTSPR1            ;More
        POPJ P,

;This routine flushes readahead.  Call before doing a spacing operation
; this doesn't actually undo the effect on the drive of the read-ahead.
; It does make sure that read-ahead's effect can't change, then returns
; in B the number of records ahead (non-negative) and in C the number of
; EOF's ahead (0 or 1).  If called twice it will return zero the second
; time.  Be sure to update your parameters.
;
MTFLRA: PUSHJ P,MTCNTR          ;Make sure user space is writable first
        MOVSI B,%MASTP
        MOVSI T,%MARAC
        IORM B,MSRAC(W)         ;Tell PI-level read routine to stop reading
        TDNE T,MSRAC(W)         ;Wait until PI level actually stops
         PUSHJ P,UFLS
        ANDCAM B,MSRAC(W)       ;Turn off %MASTP, things are now quiet
        SKIPLE MSCMDC(W)        ;Make sure PI level is completely inactive
         PUSHJ P,UFLS           ;Wait if necessary
        MOVE B,MSNBOL(W)        ;Get # bufs on read list (='s # records ahead)
        LDB C,[.BP (%MAEFA),MSRAC(W)] ;1 if EOF read ahead
        MOVSI T,%MAEFA          ;Clear read-ahead EOF 
        ANDCAM T,MSRAC(W)
        JRST MTCBFF             ;Go flush read-ahead buffers
\f
;Space files, + = forward, - = back
MTSPF:  SKIPE MSCRW(W)          ;Not allowed if writing
         JRST MTSOSP
        PUSHJ P,MTFLRA          ;Flush read-ahead
        MOVN B,C                ;Number of files tape is ahead of user
        ADDB B,MTMCNT(W)        ;Adjust desired count
        JUMPE B,CPOPJ           ;If now zero we are done
MTSPF1: PUSHJ P,MTCNTR          ;Update user's count in case of PCLSR
        JUMPG B,MTSPFF          ;Go do forward if needed
        MOVEI B,MGSPRF          ;Get space reverse file command
        PUSHJ P,MTCMD           ;Queue it
        AOSGE B,MTMCNT(W)       ;Done?
         JRST MTSPF1            ;Nope
        POPJ P,

MTSPFF: MOVEI B,MGSPFF          ;Get space forward file command
        PUSHJ P,MTCMD           ;Do it
        SOSLE B,MTMCNT(W)       ;Count down
         JRST MTSPF1            ; till done
        POPJ P,

;Update user's FUNCTION,,COUNT word in case he's PCLSR'd
;
MTCNTR: HRRZ A,MTMTAP(W)
        MOVE T,MTMFNC(W)
        HRL T,MTMCNT(W)
        XCTR XW,[MOVEM T,(A)]
        POPJ P,

;Get Controller status words to I,J
;
MTSTAT: SKIPLE MSCMDC(W)        ;Wait till commands queued to PI level are done
         PUSHJ P,UFLS
        MOVEI B,MGSTAT          ;GET STATUS command
        PUSHJ P,MTCMD           ;Give to PI
        SKIPLE MSCMDC(W)        ;Wait till done
         PUSHJ P,UFLS
        MOVE I,MGCMTC(W)
        MOVE J,MGCMTS(W)
        POPJ P,

;Go to EOT
;
MTSPEOT:MOVEI B,MGSEOT          ;Get SPACE-TO-LOGICAL-EOT command
        JRST MTCMD              ;Queue it. Note read-ahead doesn't matter here

;Stop whatever we are doing right now
; Very brute-force - throws away all pending commands, read-ahead buffers, etc.
;
MTSTOP: CONO PI,UTCOFF          ;We are going to mess with buffer lists
        SETZM MSCMDC(W)         ;Poof, no more commands
        MOVE Q,[-MGQDLL,,MGQD0-1] ;Reset Q PDL pointer to base of stack
        MOVE T,MSLCTB
        IMUL T,W
        ADD Q,T
        MOVEM Q,MGQDLP(W)
        MOVE Q,[-MSCBL-1,,MSCB0-1] ;Reset command queue input pointer
        ADD Q,T
        MOVEM Q,MTCMBP(W)
        MOVE Q,[4400,,MSCB0-1]  ;Reset command queue output pointer
        ADD Q,T
        MOVEM Q,MGCMBP(W)
        SKIPL A,MTMDN(W)        ;Buffer active at MP level?
         PUSHJ P,IMEMR          ;Yes, release it
        SETOM MTMDN(W)          ;No buffer active at MP level
        SETZM MSMPRP(W)         ;Zero MP pointer into current buffer
        SETZM MSMPRC(W)         ;Zero count of available words in buffer
        PUSHJ P,MTCBFF          ;Flush any buffers queued for PI level
        CAME W,MGUNIT           ;Is interrupt level waiting for this unit?
         JRST UTCONJ            ;No, all set
        SETOM MGUNIT            ;Yes, say no unit waiting for interrupt.
                                ;(Makes interrupt go away w/out doing anything)
IFN TM10P,[
        CONI MTC,I              ;See what drive controller thinks it's using
        LDB B,[MUNITF,,I]
        CAME W,B                ;Same as the drive we're clearing?
         JRST UTCONJ            ;If not same unit, don't do anything
        MOVE B,MTCONO(W)        ;Yes, abort operation in progress
        CONO MTS,31             ;Stop the tape
        CONO MTC,(B)            ;Clear interupts
];IFN TM10P
IFN TM03S,[
        IORDI B,%TMTC
        ANDI B,7                ;Get selected transport
        CAME W,B                ;Same?
         JRST UTCONJ
        PUSHJ P,TMINIC          ;Yes, go reinit controller
];IFN TM03S
        SKIPGE A,MGCABN(W)      ;Any buffers active at PI level?
         JRST UTCONJ            ;No
        PUSHJ P,IMEMR           ;Yes, return buffer to system
        SETOM MGCABN(W)         ;Say no buffer active at PI level
        JRST UTCONJ             ;Leave


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