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-4lists diskette drive signals by mnemonic name and provides the function.

TABLE C-4Diskette 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.

 

 

Appendix C Functional Description C-17

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Sun Microsystems 60 service manual Table C-4Diskette Drive Signals and Functions