Signal Line Description; Input Control Lines - HP 9130K Service Manual

Signal Line Description
Input Control Lines
Drive Select Lines
Interface Information
2-3
There are four drive select lines which are used for selecting and de-selecting one of three
disc drives attached to the controller.
When the logic level on the drive select line is low, the disc drive electronics are enabled and
the drive will respond to step or Read/Write commands.
The drive select line must remain stable in the low state until the step or Read/Write
command is completed.
When the logic level on the drive select lines are high, the input control lines and output
status lines are disabled.
There is also a user installed option jumper available to utilize a fourth drive select line.
The disc drive address is determined by a select code shunt block located on the drive
electronics circuit board. The drive select lines 1 through 3 provide a means of daisy
chaining a maximum of three disc drives to a controller. An undefined operation may result
if more than one drive is assigned the same select code or if more than one of the drive
select lines are low simultaneously.
Motor On
A low logic level on this line causes the drive motor to accelerate and stabilize in less than
250 msec. When this line goes high, the drive motor decelerates to a stop.
Direction Select and Step Lines
When a disc drive is selected, a low pulse greater than 1 /-Lsec. but less than 2 msec.
appearing on the step line initiates head assembly motion. The direction of this motion is
determined by the logic level appearing on the direction select line when the step pulse is
issued. A high logic level on the direction select line when the step pulse is issued the
direction of motion is outward (step-out) away from the center of the disc. A logic low on the
direction select line results in the inward direction (step in) of motion toward the disc center.
To ensure proper positioning, the direction select line should be stable 1 msec. minimum
prior to the step pulse and remain stable until 1 /-Lsec. after the step pulse. The access
motion is initiated on the trailing edge of the step pulse.
Consecutive trailing edges of step pulses should not be less then 5 msec. apart.
The drive electronics will ignore step pulses if any of the following conditions exist:
• The write gate line is low.
• The direction select is high and the head position is at track O.
• The drive is not selected.