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2803 TAPE CONTROL (Continued)
Sense Byte 3 (Cont'd)
Bit
Name
Description
3
CRC
A cyclic redundancy check occurred
during a read or read backward
operation.
4
Skew Register A character with incorrect parity
VRC
detected in skew register during
write, write tape mark, and
erase operation.
5
1, 600 BPI set in TU.
6
Backward
7
C Compare
C compare is an equipment check.
NOTE:
Data checks include bits 0-4. Any will set data check in
sense byte 1 (bit 4).
Sense Byte 4
Bit
Name
Description
0
Echo
The tape unit failed to generate an
echo pulse in response to a write
pulse.
Reject TU
Selected tape unit failed to respond
to set read or set write status when
instructed, or became not ready
during execution of a tape motion
operation.
2, 3,
Read Clock,
Associated clock has malfunctioned.
4
Write Clock,
Delay Counter
5, 6,
Sequence
These indicators are maintenance
7
Indicators G,
aids. They set only in the event of
B, and A
a machine failure and cause a unit
check.
NOTE:
Sense byte 4 and bit 7 of sense byte 3 are equipment
checks and are normally the result of machine failure.
IBM CONFIDENTIAL
S/360
85
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