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3.
UNIT SELECT 1,2
Two unit select lines are used by the controller to select the appropriate drive. These
two lines are mutually exclusive; only one drive can be selected at a time. The lines
must remain active during any command from the controller. Logical Unit assignment
is accomplished by means of the unit select jumpers on the drive Printed Circuit Board
and the appropriate signal adapter PCB attached to the drive (either drive 0 or 1).
4.
WRITE ENABLE
-
_^—~ —
]
To enable the FDD write driver, this line is held at a logic 1.
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To disable the FDD write driver and enable the FDD read circuitry, this line is held at
logic 0.
5.
WRITE FAULT RESET
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A logic 1 level on this line clears the Write Fault Latch. This signal is not used on the
SA 800-1 drive.
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6.
WRITE DATA (REFER TO FIGURE 5-3)
*
*
*
This line contains the double-density encoded Write Clock and Data information to
the FDD. The Write Clock and Data Pulses must be 250 nanoseconds + 20% in length
and are true at the logic 1 level. Information to be recorded on the disk is derived
from the leading edge of each pulse (i.e., at the logic 0 to logic 1 transition point).
7.
LOW CURRENT
-
-
- —
A logic 1 level on this line causes reduced write current to be used during a write
operation. Low current should be true for all tracks greater than 43 (inner tracks).
It is not necessary to gate low current with write enable in the controller. This
signal is not used on the SA 800-1 drive.
5-5
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