BLKPTR	;BLKI/BLKO POINTER.
DMPPTR	;DUMP MODE BLKI/BLKO POINTER MOVED TO BLKPTR AT INTERRUPT
DMPLST	;RELATIVE POINTER TO CURRENT DUMP MODE COMMAND LIST WORD
DTOTAL	;TOTAL ERROR COUNT FOR SYSTEM SINCE IT WAS LOADED
	;(COUNT NOT CLEARED AT SYSTEM INITIALIZATION)
DFTOTAL	;TOTAL FATAL ERROR COUNT FOR SYSTEM SINCE LOADED
	;I.E., OPS THAT FAILED DTTRY (USUALLY 3) TIMES
DTTAC	;PLACE TO SAVE TAC ON DC CHANNEL
DTUNIT	;DT UNIT IN BITS 30-32, DT PIA BITS 33-35
ERRFLG	;DATA MISSED BY DC IF NON-ZERO
RBNCNT	;COUNT DOWN NUMBER OF REVERSALS SEEKING BLOCK
UBUF	;ABS. ADR. OF SECOND WORD OF USER BUFFER
UERRCN	;NO. OF ERROR SO FAR ON THIS OPERATION
DTTAC1	;TEMP CELL FOR CH1
USVDB	;DDB ADDRESS FOR CURRENTLY ACTIVE UNIT
BLKCNT	;COUNT OF NO. OF BLOCKS WHICH CURRENT JOB
	;USING DECTAPES CAN DO BEFORE HAVING TO GIVE
	;DTC TO ANOTHER JOB IF ONE IS WAITING
	;THIS IS SETUP AT UUO LEVEL AND DECREMENTED AT
	;JOB DONE TIME AT INTERRUPT LEVEL
	;IF TAPE MUST SEARCH FOR BLOCK, COUNT IS SET TO ZERO
	;MEANING THAT QUANTUM IS EXCEEDED IMMEDIATELY
UBKN	;BLOCK NUMBER FOR BN SEARCH
BNDISP	;DISPATCH WHEN CORRECT BN IS FOUND
CONSZ1	;DTS ERROR MASK (116 FOR BUFFERED MODE, 16 FOR DUMP)
RDBN	;JSR HERE FOR BN XFER DURING BN SEARCH
WTRV	;JSR HERE FOR DATA XFER FOR WRITE BLOCK IN REVERSE
RDRV	;JSR HERE FOR DATA XFER FOR READ BLOCK IN REVERSE
ENPT1	;JSR HERE TO STOP TAPE.  DON'T DISMISS INT!
ENPT	;JSR HERE (FORWARD, BUFFERED I/O) TO STOP TAPE.
DMPADV	;JSR HERE WHEN ONE DUMP MODE COMMAND WORD EXHAUSTS
DCLOC	;ADDRESS OF THE BLKI/O LOCATION
DCLOC1	;ADDRESS OF THE JSR LOCATION (ABOVE PLUS 1)