HP 7942 Service Manual page 20

Channel In terf ace
7942 and 7946
Table 2 -1. Device Command Summary
LOCA TE AND READ
(REAL TIME)
FUNCTION:
OPCODE:
FORMAT:
Locates the data indicated by the target address and trans-
mits the data to the host.
No variables or parameters
LOCA TE AND WRITE
(REAL TIME)
FUNCTION:
OPCODE:
FORMAT:
Tranfers data from the host for storage beginning at the ad-
dress specified by the target address.
No variables or parameters
LOCA TE AND VERIFY
(GENERAL PURPOSE)
FUNCTION:
OPCODE:
FORMAT:
Instructs the device to perform an internal verification of a
section of data to ensure that it can be read.
No variables or parameters
SPARE BLOCK
(GENERAL PURPOSE)
FUNCTION:
OPCODE:
FORMAT:
2-2
Gives the device permission to become temporarily busy while
sparing the block indicated by the target address.
<00000110> <OOOOOSOT>Pl
P1
=
sparing mode byte
S
=
0 skip spare S
=
1 jump spare
T
=
0 retain data T
=
1 do not retain data
T must equal 1 for tape operation
S must equal 0 for disc operation