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C	SUBROUTINE READS/WRITES 1 LINCTAPE BLOCK OF 256
C	WORDS FROM ADDRESS "IADDR" ONTO BLOCK "IBLOCK".
C	"IUNIT"=0,...,7 SPECIFIES INPUT FROM TAPE UNIT
C	"IUNIT"; "IUNIT"=8,...,15 SPECIFIES OUTPUT ONTO UNIT
C	"IUNIT"-8
C
	SUBROUTINE LTAPE(IUNIT,IADDR,IBLOCK)
S	TAD I \IUNIT
S	DCA UNIT
S	STL IAC RTL	/UNIT BITS 9&10 TO
S	AND UNIT	/AXO BITS 10&11
S	RAR
S	TAD (20		/SET EXT.ADDR.AXO
S	DCA AXO
S	TAD \IADDR	/GET 62N1 OF IADDR
S	AND (70		/INTO AXO 0-2
S	CLL RTL
S	RTL
S	RTL
S	TAD AXO
S	DCA AXO
S	TAD \IADDR#	/ADDRESS,NOT VALUE
S	DCA ADDR
S	IAC		/UNIT BIT 11 TO I-BIT
S	AND UNIT	/OF TAPE INSTRUCTION
S	CLL RTL
S	RAL
S	TAD (700
S	DCA IOINS	/FORM TAPE INSTR.
S	TAD I \IBLOCK
S	DCA BLOK	/2ND LTAPE INSTR.
S	TAD UNIT
S	AND (10		/ADD 0 OR 4 TO IOINS
S	CLL RAR		/FOR RDC(U) OR WRC(U)
S	TAD IOINS
S	DCA IOINS
S	6141		/LINC
S	1020		/LDA I
S	ADDR,0
S	23		/TMA=SET EXT.ADDR.
S	1020		/LDA I
S	AXO,0
S	1		/AXO=SET TAPE CONTROL
S	IOINS,0		/EITHER RDC U OR WRC U
S	BLOK,0		/TAPE BLOCK#
S	11		/CLR
S	1		/AXO: CLEAR EXT.OPS.
S	2		/PDP
	RETURN
S	UNIT,0
	END