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Sense Byte 6 (Tape Unit)
Bit
0
2
Designation
Seven-Track Tape Unit
Write Current Failure
Dual Density
Interpretation
Present when the selected tape unit is a seven-track unit.
This bit is never active for Models 4, 6, and 8.
Indicates that one or more write drivers have been
turned on or write bias current is flowing while the tape
unit is in read status.
Present when the selected 3420 Model 3, 5, or 7 is
capable of 1600 and 800 BPI operation or the selected
3420 Model 4, 6, or 8 is capable of 6250 and 1600 BPI
operation.
3
3420 Not Set to 1600 BPI
This bit indicates the mode of the tape unit in the
4-7
Tape Unit Model
Identification
Sense Byte 7 (Tape Unit READY-Drop Source)
Bit
Designation
0
Lamp Failure
Tape Bottom Left
2
Tape Bottom Right
3
Reset Key
4
Data Security Erase
5
Erase Head Failure
6
Air Bearing Pressure
7
Load Failure
44
3803-2/3420 Subsystem Description
following manner:
Bit 3 On:
Models
3, 5, 7
4, 6, 8
Bit 3 Off:
3, 5, 7
4, 6, 8
Mode
800 BPI, 9-track NRZI
6250 BPI
1600 BPI
1600 BPI
Bit 3 is always on for 7 track tape units.
Model
3
4
5
6
7
Bit 4
0
1
0
0
Bit 5
0
0
1
1
1
Bit 6
1
0
0
0
Bit 7
0
0
Interpretation
8
1
0
Indicates that the fiber optics lamp has failed.
Indicates that the tape bottomed in the left column.
Indicates that the tape bottomed in the right column.
Tape unit not ready because RESET was pressed, or the
door interlock was opened, after the unit had been in a
start condition.
Note: The tape unit conditions this line only if a read or
write command is executed before the RESET
pushbutton is pressed.
Indicates that a DSE is in process or was being
performed.
Notes:
1. Does not cause "ready" to drop.
2. Will not be on at normal completion of DSE (tape
unit reached TI).
No erase head current or write head bias current is
flowing in write status or erase h.ead current is flowing
while in read status.
The air bearing and/ or the machine reel hub pressure
has dropped below a critical level.
The tape unit failed to load properly.
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