C	PROGRAM MAGTAP.FT
C	-----------------
C
C
C
C	MAGTAP - A TC58 MAGTAPE HANDLER FOR OS/8 FORTRAN II.
C	---------------------------------------------------
C
C
C
C
C
C
C
	SUBROUTINE MAGTAP(NUMB,ADDR,JCMD,IFLAG,IBYTE,IUNIT)
C
C
C	RAY GLASS AND PETER LEMKIN
C	NATIONAL INSTITUTES OF HEALTH
C	BETHESDA, MD. 20014
C
C	OCTOBER 11, 1972
C	REVISED DEC 4, 1972
C
C
C	ABSTRACT
C	------------
C	"MAGTAP" IS AN OS/8  FORTRAN II SUBROUTINE WHICH
C	ENABLES THE USER TO CONTROL EITHER A TU10
C	OR A TU20 9 TRACK MAGTAPE DRIVE UTILIZING
C	THE TC58 CONTROLLER. THIS MAGTAPE DEVICE HANDLER
C	ALLOWS THE USER TO READ, WRITE, READ-COMPARE,
C	SPACE BACKWARDS, SPACE FORWARD, WRITE END OF FILE,
C	CHECK FOR BEGINING OR END OF TAPE, CHECK
C	FOR END OF FILE MARK, AND REWIND THE TAPE. MAGTAP RUNS
C	WITH INTERRUPTS OFF.
C
C
C
C
C**PAGE
C	I.INTRODUCTION
C	------------
C	"MAGTAP" IS AN OS/8  FORTRAN II SUBROUTINE WHICH
C	ENABLES THE USER TO CONTROL EITHER A TU10
C	OR A TU20 9 TRACK MAGTAPE DRIVE UTILIZING
C	THE TC58 CONTROLLER. THIS MAGTAPE DEVICE HANDLER
C	ALLOWS THE USER TO READ, WRITE, READ-COMPARE,
C	SPACE BACKWARDS, SPACE FORWARD, WRITE END OF FILE,
C	CHECK FOR BEGINING OR END OF TAPE, CHECK
C	FOR END OF FILE MARK, AND REWIND THE TAPE.
C	MAGTAPE RUNS WITH INTERRUPTS OFF. HOWEVER, BY A MINOR
C	MODIFICATION, THE "TINT" ROUTINE COULD BE USED TO SERVICE 
C	MAGTAP INTERRUPTS.
C
C
C
C
C
C
C
C	II.EXAMPLE OF USING MAGTAP
C	----------------------
C	AN EXAMPLE OF A CALL TO MAGTAP IS GIVEN BELOW:
C
C		"CALL MAGTAP(200,ADDR,4,IFLAG,0,1)"
C
C	THIS CALL WILL CAUSE 200 DECIMAL PDP8 WORDS TO BE WRITTEN
C	ON MAGTAPE UNIT 1, FROM LOCATION "ADDR". THE WORD
C	"ADDR" IS THE LOCATION OF THE FORTRAN ARRAY IN
C	THE PDP8. THE 4 IS THE COMMAND TO WRITE DATA ONTO
C	THE MAGTAPE. THE WORD 'IFLAG'	IS SET TO 0
C	OR -1 BY THE MAGTAP SUBROUTINES, AND IS
C	USED AS A FLAG TO SIGNAL IF A TEST IS TRUE
C	OR FALSE. THE NEXT TO LAST ARGUMENT, 0, INDICATES
C	THAT BYTE MODE IS TO BE USED WHEN WRITING ONTO
C	THE MAGTAPE. THE LAST ARGUMENT, 1, INDICATES UNIT 1 IS
C	TO BE USED.
C
C
C
C
C
C
C	III.ARGUMENT LIST
C	-------------
C
C	NUMB	/THE NUMBER OF WORDS TO BE TRANSFERED
C		/TO OR FROM THE MAGTAP. 4096
C		/WORDS OR BYTES, IS THE MAXIMUM SIZE
C		/FOR THE ARGUMENT 'NUMB'.
C
C	ADDR	/THE FORTRAN VARIABLE ARRAY USED TO
C		/SPECIFY WHERE DATA IS READ OR WRITTEN.
C
C	JCMD	/THIS COMMAND RANGES OVER 0 TO 13.
C		/AND DISPATCHES THE FUNCTION SPECIFIED
C		/IN THE JCMD TABLE, (SECTION IV).
C
C	IFLAG / TRUE =0,	FALSE =-1
C		/IFLAG IS SET BY TESTS JCMD=[8 THROUGH 13]
C		/THIS "FLAG" IS USED TO TEST IF COMMANDS
C		/8 THROUGH 13 HAVE A TRUE OR FALSE RESULT.
C
C	IBYTE / 0 IS BYTE MODE, -1 IS CORE DUMP MODE
C
C	IUNIT /THE UNIT NUMBER OF THE MAGTAPE DRIVE
C		/MUST BE FROM 0 TO 7.
C
C
C
C
C	DEFINITION OF BYTE MODE:
C	------------------------
C	A BYTE (THE RIGHT 8 BITS OF A PDP8 WORD WHERE)
C	BITS 0-3 ARE NOT USED.) IS TRANSFERED TO THE 9 TRACK
C	MAGTAPE AS A ONE TAPE FRAME. THIS IS CONSTRUCTED
C	IN THE FOLLOWING MANNER: BITS 1 TO 8 ARE
C	AN 8-BIT BYTE WORD, AND BIT 9 IS THE PARITY BIT.
C	THIS MEANS THAT	PDP8 BITS 4-11 ARE NOW MAGTAPE
C	BITS 1 TO 8.
C
C
C
C	CORE DUMP MODE
C	--------------
C	A PDP8 12-BIT WORD IS TRANSFERED TO THE 9
C	TRACK MAGTAPE AS TWO CONSECUTIVE 6-BIT BYTES. EACH
C	TAPE WORD IS CONSTRUCTED AS FOLLOWS:
C	BIT 9 IS USED AS A PARITY BIT, BITS 1 AND
C	2 ARE NOT USED, BITS 3 TO 6 ARE THE 6 BIT BYTE,
C	IE:THE FIRST PART OF THE 12 BIT PDP8 WORD
C	IS BITS 0-5. THE SECOND PART OF THE 12 BIT WORD
C	IS BITS 6-11.
C
C
C
C
C
C
C**PAGE
C
C	IV. JCMD COMMAND TABLE ASSIGNMENTS.
C	------------------------------
C	JCMD	FUNCTION
C	----	--------
C	0	NO OPERATION (NOP )
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:USED
C	IFLAG:IGNORED
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C	1	REWIND THE TAPE
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=1
C	IFLAG:IGNORED
C	IBYTE:IGNORED
C	IUNIT:UNIT #
C
C
C	2	READ 1 RECORD FROM THE TAPE.
C	A RECORD MAY BE ANY NUMBER OF
C	WORDS,DEPENDING ON THE SIZE OF
C	"NUMB".
C
C	NUMB:USED
C	ADDR:USED
C	JCMD:=2
C	IFLAG:IGNORED .
C	IBYTE:USED
C	IUNIT:UNIT #
C
C
C	3	READ/COMPARE 1 RECORD FROM THE TAPE.
C
C	NUMB:USED
C	ADDR:USED
C	JCMD:=3
C	IFLAG:IGNORED
C	IBYTE:USED
C	IUNIT:UNIT #
C
C	4	WRITE 1	RECORD ONTO THE TAPE.
C
C	NUMB:USED
C	ADDR:USED
C	JCMD:=4
C	IFLAG:IGNORED .
C	IBYTE:USED
C	IUNIT:UNIT #
C
C
C	5	WRITE END OF FILE
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=5
C	IFLAG:IGNORED
C	IBYTE:USED
C	IUNIT:UNIT #
C
C
C	6	SPACE FORWARD 1 RECORD.
C
C	NUMB:USED
C	ADDR:IGNORED
C	JCMD:=6
C	IFLAG:IGNORED
C	IBYTE:USED
C	IUNIT:UNIT #
C
C
C	7	SPACE REVERSE 1 RECORD.
C
C	NUMB:USED
C	ADDR:IGNORED
C	JCMD:=7
C	IFLAG:IGNORED
C	IBYTE:USED
C	IUNIT:UNIT #
C
C
C
C
C	9	TEST READ/WRITE ERROR-PARITY ERRORS.
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=9
C	IFLAG:INTERNALLY SET
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C
C	10	TEST READ/COMPARE ERROR
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=10
C	IFLAG:INTERNALLY SET.
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C	11	TEST END OF FILE MARK
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=11
C	IFLAG:INTERNALLY SET
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C
C	12	TEST BEGINING OF TAPE	MARK
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=12
C	IFLAG:INTERNALLY SET
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C	13	TEST END OF TAPE	MARK
C
C	NUMB:IGNORED
C	ADDR:IGNORED
C	JCMD:=13
C	IFLAG:INTERNALLY SET
C	IBYTE:IGNORED
C	IUNIT:IGNORED
C
C
C
C
C
C**PAGE
C
C	V. COMPILING AND LOADING
C	------------------------
C	. R FORT
C	*MAGTAP.RL,MAGTAP.LS<--MAGTAP.FT
C	.R LOADER
C	*MAIN AND ANY SUBROUTINES...
C	*MAGTAP.RL/0	- LOAD INTO ANY FIELD.
C	* ETC...
C	*LIB8/L$
C	.SAVE SYS:MAIN ETC...
C
C
C
C	VI. ADDITIONAL INFORMATION
C	----------------------
C	FOR A COMPLETE DESCRIPTION OF WHICH
C	MAGTAPE COMMANDS MUST BE USED AND WHICH
C	COMMANDS MAY BE IGNORED FOR ANY CALL
C	TO THIS SUBROUTINE SEE: INSTRUCTION MANUAL
C	------------------
C	MAGNETIC TAPE CONTROL-TC58, SECTION 2.6
C	---------------------------------------
C	OF DEC-08-I4AA-D , MARCH 1968.
C	-------------------------------
C
C
C
C
C
C
C
C
C
C
C
C
C
C	NEW SABR OPERATORS
C	--------------------
S	OPDEF JMPI 5400 /TO PREVENT EXTRA CODE
S	OPDEF DCAI 3400	/TO PREVENT DUMMY SABR INDIRECTS
S	OPDEF MTAF 6712	/CLEAR THE STATUS AND COMMAND REGISTOR
S	OPDEF MTLC 6716	/LOAD THE CONTENTS OF AC0-11 INTO
C	/THE COMMAND REGISTOR
S	OPDEF MTGO 6722	/EXECUTE THE COMMAND IN THE COMMAND
C	/REGISTOR
S	OPDEF MTRS 6706	/READ CONTENSE OF STATUS REGISTOR
S	SKPDF MTCR 6711	/SKIP ON TAPE CONTROLL READY
S	SKPDF MTSF 6701	/SKIP ON ERROR FLAG OR MAGTAP FLAG
S	SKPDF MTTR 6721	/SKIP ON TAPE TRANSPORT READY
C
C
C
C
C
C**PAGE
C	------------------------------------------------------
C
C
C	1.0 CALL BY VALUE, AND INITIALIZATION.
	ICMD=JCMD
	IDEV=1
C
C
C
C
C	1.2 THE COMMAND TELLS THE MAGTAPE WHAT TO DO.
C	IT IS INTERPRETED BY THE MAGTAPE ROUTINE IN ORDER TO
C	CONTROL THE MAGTAPE (MTA).
C	READ,REWIND,WRITE, ETC.
C
C
C
C
C
C
C	2.IS COMMAND MINUS ?
	IF(ICMD)2,3,3
2	WRITE(IDEV,902)ICMD
	RETURN
902	FORMAT(5X,'BAD MAGTAP COMMAND. ICMD=',I5)
C
C
C
C
C
C
C	3.TEST IF A MAGTAPE COMMAND OR TNTX COMMAND
3	IF(ICMD-7)4,4,500
S\4,	TAD \ICMD
S	RTL;RAL
S	DCA \ICMD
	IF(IBYTE)41,40,41
C
C
C
C
C
C	4.BYTE MODE O4O7 IS THE CONTROL WORD.
S\40,	TAD (0407
S	DCA \KBYTE
	GOTO 42
C
C
C
C
C
C	5.DUMP MODE O6O7-IS THE CONTROL WORD.
S\41,	TAD (0607
S	DCA \KBYTE
C
C
C
C
C
C	6.SET UP THE WORD COUNT AND THE CURRENT ADDRESS
C	REGISTERS.
S\42,	TAD I \NUMB
S	CIA
S	CPAGE 3
S	6201 /CDF 0
S	DCAI (7752 /PUT IN WC
C	FAKE A CDF
S	JMS 45 /CDFSKP
S	CLA
S	TAD \ADDR /GET THE FIELD
S	AND (0070
S	DCA BFIELD /DATA FIELD
S	STA /LOAD -1
S	TAD \ADDR# /GET THE ADDRESS
S	CPAGE 3
S	6201 /CDF 0
S	DCAI (7753 /CURRENT ADDRESS
C	FAKE IT AGAIN
S	JMS 45 /CDFSKP
S	CLA
C	GET THE COMMAND
S	TAD \ICMD
S	AND (0070	/MAKE SURE
S	TAD \KBYTE	/COMMAND MASK
S	DCA COMMAND
C	CHECK IF IUNIT IS LEGAL (0 TO 7)
	IF(IUNIT-7)63,63,64
64	WRITE(IDEV,65)IUNIT
65	FORMAT('IUNIT MUST BE FROM 0 TO 7 : ',I5)
	RETURN
C
C	MOVE IUNIT INTO BITS 0 TO 2 FOR UNIT SELECTION.
S\63,	CLA
S	TAD I \IUNIT
S	RTL;RTL;RTL /LEFT SHIFT 6 BITS
S	RTL;RAL /LEFT SHIFT ANOTHER 3
S	AND (7000	/MAKE SURE BITS 0 TO 2
S	TAD COMMAND /FORM THE COMMAND
S	DCA COMMAND	/FORM COMMAND, READY FOR COMMAND REG.
C
C
C
C
C
C	7.GO EXECUTE THE COMMAND
S	CPAGE 5
S	JMS GOTAPE
SCOMMAND,	0 /COMMAND FORMED FROM ICMD & COMMAND MASK.
SBFIELD,	0 /DATA BUFFER FIELD FROM ADDR.
C
C
C
C
C
C	8.WAIT FOR TAPE TO FINISH EXECUTING THE COMMAND.
S	CPAGE 2
S	JMS WTRDY
	RETURN
C
C
C
C
C
C
C
C	****************
C	INTERNAL SUBROUTINE WTRDY
C	IS USED TO WAIT UNTIL THE MAGTAP IS
C	READY.
C	CALLING SEQUENCE:
C	JMS WTRDY
C	RETURNS HERE WHEN READY.
SWTRDY,	0
SWTTT,	MTCR	/IS CONTROL READY
S	JMP WTTT	/NO
S	MTTR	/IS THE DRIVE READY
S	JMP WTTT /NO
S	JMPI WTRDY	/YES RETURN
C
C
C
C
C
C
C
C	********************
C	INTERNAL SUBROUTINE GOTAPE
C	IS CALLED BY MAGTAP TO EXECUTE THE
C	TAPE COMMAND.
C	CALLING SEQUENCE:
C	JMS GOTAPE
C	COMMAND
C	FIELD
C	RETURN
C
C
S	CPAGE 23
SGOTAPE,	0	/PERFORM THE TAPE OPERATION.
S	MTAF	/CLEAR TAPE CONTROL REGISTERS.
S	TAD I GOTAPE	/GET THE COMMAND.
S	MTLC	/LOAD THE COMMAND.
S	ISZ GOTAPE
S	CLA
S	CLA
S	TAD I GOTAPE	/GET THE BUFFER FIELD.
S	MTGO	/GO DO IT.
SMTARDY,	MTSF
S	JMP MTARDY
S	JMS TINT	/GET THE STATUS OF THE MACHINE.
S	ISZ GOTAPE
S	JMPI GOTAPE	/RETURN
C
C
C
C
C
C
C
C	*********************
C	INTERNAL SUBROUTINE TINT
C	IS USED TO SERVICE THE MAGTAP FAKE INTERUPT.
C	IT ACTUALLY SIMULATES THE SERVICING OF THE MTA
C	INTERUPT, SINCE NOT ACTUALLY AN INTERUPT.
C	IT SAVES THE STATUS OF THE MAGTAP AT THE
C	TIME OF INTERRUPT AND CLEARS THE COMMAND
C	AND INTERRUPT REGISTERS.
C	SERVICE THE MAGTAPE
S	CPAGE 15
STINT,	0
S	CLA CLL
S	MTRS	/READ MTA STATUS REGISTERS.
S	DCA TSTAT
S	6724	/GET THE COMMAND REGISTER.
S	DCA TCOM
S	MTAF	/CLEAR STATUS AND COMMAND REGISTERS.
S	JMPI TINT	/RETURN
C
STCOM,	0
STSTAT,	0
C
C
C
C
C
C
C
C	***************************
C	INTERNAL SUBROUTINE TNTX
C	SENSES THE TAPE CONDITION-THIS ROUTINE IS CALLED
C	BY THE USER,TO DETECT ERRORS,END OF FILE CONDITION
C	BEGINING OR END OF TAPE. IN ORDER FOR IT TO
C	WORK PROPERLY, A SIMULATED INTERUPT MUST HAVE
C	BEEN PROCESSED BY TINT. HOWEVER, IF
C	TNTX IS CALLED WHILE THE TAPE IS STILL BUSY
C	IT WILL WAIT FOR TAPE TO BECOME READY.
C	BY WHICH TIME AN INTERRUPT SHOULD HAVE BEEN
C	FIELDED.
C	RESULT OF TNTX
C	--------------
C	IFLAG=0	IS TRUE
C	IFLAG=-1	IS FALSE
C
C
C
C
C
C	1.IF ICMD IS GREATOR THAN 13 WE HAVE AN
C	ERROR IN THE COMMAND.
500	IF(ICMD-13)501,501,2
501	IFLAG=0
C
C
C
C
C
C	2.WAIT FOR TAPE
S	JMS WTRDY
C
C
C
C
C
C	3.GET THE COMMAND
	ICMD=ICMD-8
C
C
C
C
C
C	4.DO A TABLE LOOKUP OF THE TAPE STATUS INDEXED
C	BY ICMD.
S	TAD \ICMD
S	TAD PTCND	/I.E. THE TABLE ADDRESS.
S	DCA TN5	/INDEX OF TABLE.
S	TAD TSTAT	/GET THE STATUS.
S	CPAGE 13
S	AND I TN5	/AND IT AGAINST THE TABLE.
S	SNA CLA	/SKIP IF HOLDS.
S	JMP \503	/ERROR
	RETURN
STN5,	0
SPTCND,	TCOND
503	IFLAG=-1
	RETURN
S	CPAGE 6
STCOND,	0
S	1616	/READ/WRITE ERROR
S	1636	/READ COMPARE ERROR
S	0100	/EOF
S	1000	/BOT
S	0040	/EOT
C
C
S\KBYTE,BLOCK 1
	END