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/TD8E DECTAPE ROUTINE /VERSION 01 /JULY 2 1971 GB/RL/EF /COPYRIGHT 1971 DIGITAL EQUIPMENT CORP. / MAYNARD, MASS. /ABSTRACT-- / THE ROUTINE DESCRIBED AND LISTED HERE IS A GENERAL /DATA HANDLER FOR THE TD8E DECTAPE SYSTEM. THE ROUTINE /CONTAINS SEARCH, READ, AND WRITE FUNCTIONS IN A FORMAT /WHICH IS COMPATIBLE WITH PS/8 DEVICE HANDLER CALLING /SEQUENCES.
/THIS ROUTINE CAN BE RE-EDITED AND ASSEMBLED TO PRODUCE /VARIATIONS ON THE BASIC TD8E SYSTEM. ASSEMBLY PARAMETERS /CONTROL: /A) WHAT DRIVES (UNITS 0-7) WILL BE USED /B) THE ORIGIN OF THE TWO PAGE ROUTINE /C) WHAT MEMORY FIELD THE ROUTINE WILL RUN IN /D) THE SIZE OF THE DECTAPE BLOCK TO BE READ/WRITTEN /FOLLOWING ARE THE PARAMETERS SET UP FOR THE STANDARD /DEC VERSION OF THIS ROUTINE: DRIVE=10 /UNITS 0 AND 1 SELECTED ORIGIN=7200 /ENTRIES AT 7200 AND 7204 AFIELD=0 /INITIAL FIELD SETTING MFIELD=00 /AFIELD*10=MFIELD WDSBLK=201 /129 WORDS PER BLOCK /THE USE OF THE PARAMETERS IS AS FOLLOWS: / DRIVE: DRIVE DETERMINES WHICH UNITS WILL BE SELECTED / DRIVE=10 IMPLIES UNITS 0 &1 / DRIVE=20 IMPLIES UNITS 2&3 / DRIVE=30 IMPLIES UNITS 4&5 / DRIVE=40 IMPLIES UNITS 6&7 /ORIGIN: ALTERING ORIGIN CAUSES ASSEMBLY IN A DIFFERENT / MEMORY LOCATION. WHEN CHANGING ORIGIN KEEP IN MIND /THAT THIS IS A TWO PAGE ROUTINE. /AFIELD: AFIELD DETERMINES THE INITIAL FIELD SETTING FOR THE / LOADER. PERMISSIBLE VALUES FOR AFIELD ARE 0 TO 7. /MFIELD: MFIELD IS USED IN A CIF CDF MFIELD INSTRUCTION. / THE VALUE INSERTED FOR MFIELD SHOULD BE 10(8) TIMES / THE VALUE FOR AFIELD. THE PERMISSIBLE VALUES ARE 00-70. /WDSBLK: WDSBLK GOVERNS HOW MANY WORDS THE ROUTINE THINKS ARE / IN A DECTAPE BLOCK. THE STANDARD VALUE IS 201(8) OR / 128 DECIMAL. NOTE THAT THE FUNCTION WORD BIT 10 CAN / BE USED TO SUBTRACT ONE FROM WDSBLK. THE VALUE USED / FOR WDSBLK SHOULD BE THE NUMBER OF WORDS THE TAPE WAS / FORMATTED TO CONTAIN. /IF WE WANT A HANDLER FOR UNITS 2&3 TO RESIDE IN /FIELD 2 AT LOCATION 3000 AND READ/WRITE 256(10) WORDS /PER BLOCK, THE PARAMETERS WOULD BE: / DRIVE=20 / ORIGIN=3000 / AFIELD=2 / MFIELD=20 / WDSBLK=400
/THE CALL TO THE SUBROUTINE FOLLOWS BASICALLY THE /CALLING SEQUENCE FOR PS/8 DEVICE HANDLERS. /THE CALLING SEQUENCE IS: / CDF CURRENT / CIF MFIELD /MFIELD=FIELD ASSEMBLED IN / JMS ENTRY /ENTRY=ORIGIN (EVEN NUMBERED DRIVE /AND ORIGIN+4 FOR ODD NUMBERED DRIVE. / ARG1 / ARG2 / ARG3 / ERROR RETURN / NORMAL RETURN /THE ARGUMENTS ARE: /ARG1: FUNCTION WORD BIT0: 0=READ, 1=WRITE / BITS 1-5: # BLOCKS IN OPERATION / BITS 6-8: FIELD OF BUFFER AREA / BIT 9: UNUSED / BIT 10: # OF WORDS/BLOCK. / 0= WDSBLK, 1=WDSBLK-1 / BIT 11: 1=START FORWARD, 0=REVERSE /ARG2: BUFFER ADDRESS FOR OPERATION /ARG3: STARTING BLOCK FOR OPERATION /ERRORS: THE HANDLER DETECTS TWO TYPES OF ERRORS: /A) FATAL ERRORS- PARITY ERROR, TIMING ERROR, / TOO GREAT A BLOCK NUMBER / FATAL ERRORS TAKE ERROR RETURN WITH THE / AC=4000. /B) NON-FATAL- SELECT ERROR. / IF NO PROPER UNIT IS SELECTED, THE ERROR / RETURN IS TAKEN WITH CLEAR AC. /FATAL ERRORS TRY THREE TIMES BEFORE TAKING ERROR RETURN. /THE NORMAL RETURN IS TAKEN AFTER ALL INDICATED /BLOCKS HAVE BEEN TRANSFERRED. THE AC IS CLEAR.
/THE TD8E IOT'S ARE: SDSS=7001-DRIVE /SKIP ON SINGLE LINE FLAG SDST=7002-DRIVE /SKIP ON TIMING ERROR SDSQ=7003-DRIVE /SKIP ON QUAD LINE FLAG SDLC=7004-DRIVE /LOAD COMMAND REGISTER SDLD=7005-DRIVE /LOAD DATA REGISTER SDRC=7006-DRIVE /READ COMMAND REGISTER SDRD=7007-DRIVE /READ DATA REGISTER /THE IOT'S IN GENERAL ARE 677X,676X,675X,AND 674X. /THE OTHERS CONTROL UNITS 2-7. BLOCK=DTA1 FIELD AFIELD *ORIGIN DTA0, 0 /ENTRY POINT FROM UNIT 0 CLA CLL /0 TO LINK JMP DTA1X C1000, 1000 DTA1, 0 /UNIT 2 ENTRY CLA CLL CML /1 TO LINK TAD DTA1 DCA DTA0 /PICK UP ARGS AT DTA0 DTA1X, RAR DCA UNIT /LINK TO UNIT POSITION RDF TAD C6203 /GET DATA FIELD AND SETUP RETURN DCA LEAVE TAD I DTA0 /GET FUNCTION WORD SDLD /PUT FUNCTION INTO DATA REGISTER CLL RTR /AC STILL HAS FUNCTION. PUT # WORDS PER /BLOCK INTO LINK SZL CLA /KNOCK ONE OFF WDSBLK? IAC /YES TAD MWORDS DCA WCOUNT /STORE MASTER WORD COUNT ISZ DTA0 /TO BUFFER TAD I DTA0 DCA BUFF ISZ DTA0 /TO BLOCK NUMBER TAD I DTA0 DCA BLOCK ISZ DTA0 /POINT TO ERROR EXIT CIF CDF MFIELD /TO ROUTINES DATA FIELD SDRD /GET FUNCTION INTO AC CLL RAL AND CM200 /GET # PAGES TO XFER DCA PGCT SDRD C374, AND C70 /GET FIELD FOR XFER TAD C6203 /FORM CDF N DCA XFIELD /IF=0 AND DF=N AT XFER. CLA CLL CMA RTL DCA TRYCNT /3 ERROR TRIES TAD UNIT /TEST FOR SELECT ERROR SDLC SDRC AND C100 SZA CLA JMP FATAL-1
SDRD /PUT FUNCT INTO XFUNCT IN SECOND PG. DCA I CXFUN TAD WCOUNT DCA I CXWCT SDRD /GET MOTION BIT TO LINK CLL RAR JMP GO /AND START THE MOTION. RWCOM, SDST /ANY CHECKSUM ERRORS? SZA CLA /OR CHECKSUM ERRORS? JMP TRY3 /PLEASE NOTE THAT THE LINK IS ALWAYS /SET AT RWCOM. GETCHK SETS IT. TAD PGCT /NO ERROR..FINISHED XFER? TAD CM200 SNA JMP EXIT /ALL DONE. GET OUT DCA PGCT /NEW PAGE COUNT ISZ BLOCK /NEXT BLOCK TO XFER TAD WCOUNT /FORM NEXT BUFFER ADDRESS CIA TAD BUFF DCA BUFF CLL CML /FORCES MOTION FORWARD GO, CLA CML RTR /LINK BECOMES MOTION BIT TAD C1000 TAD UNIT /PUT IN 'GO' AND UNIT # SDLC /LOOK FOR BLOCK NO. JMS I CRDQUD /WAIT AT LEAST 6 LINES TO LOOK JMS I CRDQUD CM200, 7600 /COULD HAVE SAVED A LOC. HERE SRCH, SDSS JMP .-1 /WAIT FOR SINGLE LINE FLAG SDRC CLL RTL /DIRECTION TO LINK. INFO BITS /ARE SHIFTED. AND C374 /ISOLATE MARK TRACK BITS TAD M110 /IS IT END ZONE? SNA /THE LINK STAYS SAME THRU THIS JMP ENDZ TAD M20 /CHECK FOR BLOCK MARK SZA CLA JMP SRCH SDRD /GET THE BLOCK NUMBER SZL /IF WE ARE IN REVERSE, LOOK FOR 3 /BLOCKS BEFORE TARGET BLOCK. THIS /ALLOWS TURNAROUND AND UP TO SPEED. TAD C3 /REVERSE CMA TAD BLOCK CMA /IS IT RIGHT BLOCK? SNA JMP FOUND /YES..HOORAY! M110, SZL SNA CLA /NO, BUT ARE WE HEADED FOR IT? /ABOVE SNA IS SUPERFLUOUS. JMP SRCH /YES ENDZ, SDRC /WE ARE IN THE END ZONE CLL RTL /DIRECTION TO LINK SZL CLA /ARE WE IN REVERSE? JMP GO /YES..TURN US AROUND /IF WE ARE IN THE END ZONE GOING FORWARD, IT IS AN ERROR TRY3, ISZ TRYCNT JMP GO /TRY 3 TIMES CLL CLA JMP FATAL /LINK OFF MEANS AC=4000 ON RETURN EXIT, ISZ DTA0 CLL CML /AC=0 ON NORMAL RETURN FATAL, TAD UNIT SDLC /STOP THE UNIT CLA CML RAR LEAVE, HLT JMP I DTA0
C6203, 6203 CRDQUD, RDQUAD WCOUNT, 0 BUFF, 0 MWORDS, -WDSBLK UNIT, 0 CXFUN, XFUNCT M20, -20 PGCT, 0 CXWCT, XWCT C100, 100 TRYCNT, -3 *ORIGIN+170 FOUND, SZL CLA /RIGHT BLOCK. HOW ABOUT DIRECTION? JMP GO /WRONG..TURN AROUND TAD UNIT /PUT UNIT INTO LINK CLL RAL /AC IS NOW 0 C70, 70 /********DON'T MOVE THIS!!!!****** C3, 3 TAD BUFF /GET BUFFER ADDRESS XFIELD, HLT /INTO NEXT PAGE *ORIGIN+200 XUNIT=EQUFUN CIF MFIELD DCA XBUFF /SAVE ADDRESS RAR /NOW GET UNIT # DCA XUNIT TAD XWCT DCA WORDS /WORD COUNTER REVGRD, SDSS JMP .-1 /LOOK FOR REVERSE GUARD SDRC AND K77 TAD CM32 /IS IT REVERSE GUARD? SZA CLA JMP REVGRD /NO.KEEP LOOKING TAD XFUNCT /GET FUNCTION READ OR WRITE K7700, SMA CLA JMP READ /NEG. IS WRITE WRITE, SDRC AND C300 /CHECK FOR WRITE LOCK AND SELECT ERROR CLL CML /LOCK OUT AND SELECT ARE AC 0 ERRORS SZA CLA JMP I CFATAL /FATAL ERROR. LINK MUST BE ON JMS RDQUAD /NO ONE EVER USES THIS WORD! C7600, 7600 TAD C1400 TAD XUNIT /INITIATE WRITE MODE SDLC CLA CMA JMS WRQUAD /PUT 77 IN REVERSE CHECKSUM CLA CMA DCA CHKSUM WRLP, TAD I XBUFF /GLORY BE! THE ACTUAL WRITE! JMS WRQUAD ISZ XBUFF /BUMP CORE POINTER K77, 77 /ABOVE MAY SKIP ISZ WORDS /DONE THIS BLOCK? JMP WRLP /NOT YET..LOOP A WHILE TAD XFUNCT /IS THE OPERATION FOR WDSBLK PER BLOCK? CLL RTR /IF NO, WRITE A 0 WORD SZL CLA
JMS WRQUAD /WRITE A WORD OF 0 JMS GETCHK /DO THE CHECK SUM JMS WRQUAD /WRITE FORWARD CHECKSUM JMS WRQUAD /ALLOW CHECKSUM TO BE WRITTEN JMP I CRWCOM READ, JMS RDQUAD JMS RDQUAD JMS RDQUAD /SKIP CONTROL WORDS AND K77 TAD K7700 /TACK 7700 ONTO CHECKSUM. DCA CHKSUM /CHECKSUM ONLY LOW 6 BITS ANYWAY RDLP, JMS RDQUAD JMS EQUFUN /COMPUT CHECKSUM AS WE GO DCA I XBUFF /IT GETS CONDENSED LATER ISZ XBUFF C300, 300 /PROTECTION ISZ WORDS /DONE THIS OP? JMP RDLP /NO SUCH LUCK TAD XFUNCT /IF OP WAS FOR WDSBLK-1, READ AND CLL RTR /CHECKSUM THE LAST TAPE WORD SNL CLA JMP RDLP2 JMS RDQUAD /NOT NEEDED FOR WDSBLK/BLOCK JMS EQUFUN /CHECKSUM IT RDLP2, JMS RDQUAD /READ CHECKSUM AND K7700 JMS EQUFUN JMS GETCHK /GET SIX BIT CHECKSUM JMP I CRWCOM WRQUAD, 0 /WRITE OUT A 12 BIT WORD JMS EQUFUN /ADD THIS TO CHECKSUM SDSQ /SKIP ON QUADLINE FLAG JMP .-1 SDLD /LOAD DATA ONTO BUS CLA /SDLD DOESN'T CLEAR AC JMP I WRQUAD RDQUAD, 0 /READ A 12 BIT WORD SDSQ JMP .-1 SDRD /READ DATA JMP I RDQUAD
EQUFUN, 0 /COMPUTE EQUIVALENCE CHECKSUM CMA DCA EQUTMP /ACTUALLY CHECKSUMS ON DECTAPE ARE TAD EQUTMP /EQUIVALENCE OF ALL WORDS IN A RECORD AND CHKSUM /SIX BITS AT A TIME. BUT SINCE EQUIVALENCE CIA /IS ASSOCIATIVE, WE CAN DO IT 12 CLL RAL /BITS AT A TIME AND CONDENSE LATER. TAD EQUTMP /THIS ROUTINE USES THESE IDENTITIES: TAD CHKSUM /A+B=(A.XOR.B)+2*(A.AND.B) DCA CHKSUM /A.EQU.B=.NOT.(A.XOR.B)=A.XOR.(.NOT.B) TAD EQUTMP /A.EQU.B=(A+(.NOT.B))-2*(A.AND.(.NOT.B)) CMA JMP I EQUFUN GETCHK, 0 /FORM 6 BIT CHECKSUM CLA TAD CHKSUM CMA CLL RTL RTL RTL JMS EQUFUN CLA CLL CML /FORCES LINK ON AT RWCOM TAD CHKSUM AND K7700 JMP I GETCHK CFATAL, FATAL CRWCOM, RWCOM XFUNCT, 0 CM32, -32 C1400, 1400 CHKSUM, 0 WORDS, 0 XBUFF, 0 XWCT, 0 EQUTMP, 0 $$$$$$$$$$$
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