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Appendix C Functional Description C-17
standby mode. The diskette drive is connected to the SCSI backplane with a 34-pin
ribbon cable. The maximum cable length is 1.5 meters. From the SCSI backplane, the
diskette drive is cabled to the motherboard with the SCSI connections.
Diskette Drive Signals
TABLE C-4 lists diskette drive signals by mnemonic name and provides the function.
TABLE C-4 Diskette Drive Signals and Functions
Signal Name Function
MODE_SELECT When active low, MODE_SELECT sets the
drive for a 1.2-Mbyte formatted disk. When
active high, MODE_SELECT sets the drive
for a 1.44-Mbyte formatted disk.
HIGH_DENSITY_IN_L When active low, HIGH_DENSITY_IN_L
indicates that a high-density disk is
inserted into the drive.
NDEX When active, INDEX indicates the
beginning of each track. An active pulse is
sent for each disk rotation.
DRIVE_SELECT When set true, DRIVE_SELECT enables the
drive to respond to other input signals.
MOTOR_ENABLE When set low, MOTOR_ENABLE initiates
the spindle motor rotation.
DIRECTION When active high, DIRECTION indicates
movement of the magnetic head assembly
toward the outer cylinders. When active
low, indicates movement of the magnetic
head assembly toward the inner cylinders.
STEP On the trailing edge, STEP moves the
magnetic head in the direction specified by
DIRECTION at a rate of one cylinder per
pulse.
WRITE_DATA WRITE_DATA supplies the disk drive with
the data to be written to disk provided the
WRITE_GATE signal is active low.
WRITE_GATE When active low, WRITE_GATE enables the
drive write circuits. When active high,
WRITE_GATE enables drive read circuits.