Sense Byte 2 (Track In Error) - IBM 3803 Manual

Bit Designation Interpretation
2
3
4
5
6
7
TU Status B
TU Status A#
Off
Off
On
TU status B is set when an addressed tape unit is not
ready. Assuming no outstanding device end status, bits
and 2 determine response to initial selection as follows:
Response to
TU Status B# TU Status Initial Selection*
Off
Non-existent
Unit Check**
On Not ready, arm Unit Check**
For Device End
Off Ready and not Clean status
rewinding
* If the stack flag is off and no Device End is outstanding.
** Unit Check is not signaled for a sense operation. Following a Unit Check (due to
Non-existent or Not ready) or Busy indication, Device End is signaled when the
tape unit becomes ready and not rewinding or switched.
# In the 2400-series, TU status A and TU status B are lines from the tape unit.
They do not exist on the 3803/3420 subsystem and are logically constructed by the
tape control from the tape unit responses.
Seven Track
Load Point
Write Status
File Protect
Not Capable
Seven Track is set when the selected tape unit has the
seven-track f ea tu re.
Load Point is set when the selected tape unit is at the
beginning of a tape.
Write Status is set when the selected tape unit is in write
status.
File Protect is set when the selected tape unit is in file
protect status.
Not Capable is set when:
1. Leaving load point and a Read or Forward Space
command scanning the load point area for a format
burst finds that the tape unit feature, tape control
feature, and tape format do not agree. Tape motion
is halted. Channel End, Device End, and Unit Check
are signaled in the status byte for Read operations,
and Control Unit End, Device End, and Unit Check
are set for Forward Space operations.
Note: Following a Read Not Capable, tape is positioned
away from load point with the read head located
between the identification burst area and the first data
block on tape.
2. On a Write operation if the density retained in the
tape unit does not match the capability of the tape
control.
Sense Byte 2 (Track In Error)
This sense byte contains the track-in-error
(TIE)
indicator bits that are set at the
end of a Read, Read Backward, Write, or Loop-Write-To-Read
(LWR)
command.
For nine-track
NRZI
operations:
Write or
LWR
has bits 6 and 7 on.
In read or read backward operations:
1. A single bit and data check indicate the track in error.
2. Bits 6 and 7 with Data Check indicate an uncorrectable error pattern.
3. Bits 6 and 7 without Data Check indicate normal operation.
Section 4: Status and Sense Information
41