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
TABLEC-4 lists diskette drive signals by mnemonic name and provides the function.
TABLEC-4 Diskette Drive Signals and Functions
SignalName Function
MODE_SELECT When active low,MODE_SELECT sets the
drivefor 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 Whenset true, DRIVE_SELECT enables the
drive to respondto 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
towardthe outer cylinders. When active
low,indicates movement of the magnetic
head assembly towardthe inner cylinders.
STEP On the trailing edge, STEP moves the
magnetic head in the directionspecified by
DIRECTION at a rate of one cylinder per
pulse.
WRITE_DATA WRITE_DATAsupplies the disk drive with
the data to be written to disk providedthe
WRITE_GATEsignal is active low.
WRITE_GATE When active low, WRITE_GATEenables the
drive write circuits.When active high,
WRITE_GATEenables drive read circuits.