Sense Byte 3 (Data And Equipment Checks) - IBM 3803 Manual

For seven-track
NRZI
operation:
During seven-track read or read backward operations, the track-in-error byte
is used for tape unit sense level control. The values are:
Normal - no read YRC error
1st read YRC error
2nd read YRC error
3rd error will return to normal and
continue to cycle as shown above.
TIE
00
80
40
Sense Byte 3 (Data and Equipment Checks)
Bit
0
2
3
4
5
6
42
3803-2/3420 Subsystem Description
Designation
Read/Write Vertical
Redundancy Check
Multiple Track
Error /Longitudinal
Redundancy Check
Skew Error
End Data Check/Cyclic
Redundancy Check
Envelope/Error
Correction Check
1600 BPI set in TU
Backward
j
Interpretation
R/W YRC is set:
6250 When in error correction mode and the
track(s) in error cannot be found.
1600 When there is a YRC error without a dead
track or phase error.
NRZI
6250/
When a YRC occurred during a read or read
backward operation or a missing byte is
detected. Also set on a seven-track write
operation if a missing byte is detected.
1600 When multiple tracks in error are detected.
NRZI Present when a Longitudinal Redundancy
Check occurred during a read, read backward,
write, or write tape mark operation.
Present when excessive skew was detected on a 6250 BPI
or 1600 BPI write, read, or read backward operation or
a NRZI write operation.
Set in 6250/1600 BPI mode if a track fails to start.
1600 BPI read operations if the ending marker is not
detected, or if the postamble has less than six or more
than 50 bytes.
All write operations when a CRC error occurs.
6250 or 800 BPI nine-track read operations when a CRC
error occurs.
ENV /ECC is set:
6250 When any track signal falls below the threshold
on a read or write operation. This does not set
Data Check.
1600 When there is a phase error or any track falls
below the threshold on a read or write
operation. This sets Data Check on write only.
NRZI When a byte with incorrect parity is detected
during a write or write tape mark operation.
Set when the selected tape unit is in phase-encoded
mode.
Backward is set when the selected tape unit is in
backward status.