Output Status Lines - HP 9130K Service Manual

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Interface Information
Composite Write Data
When the disc drive is selected, this line provides the bit serial composite write data pulses
that control the switching of the write current in the selected head. The write electronics
must be enabled by the write gate line.
Write Gate
When this line is low, the write electronics are enabled for writing data (read electronics are
disabled). This line enables write current to flow in the selected read/write head.
Data is written under the control of the composite write data line and side one select line.
Changes of state on the write gate line should occur before the first write data pulse. When
the write gate line is high, all write electronics are disabled.
If a write protected disc is installed; the write electronics are disabled irrespective of the state
of the write gate and side one select lines.
Side One Select
The Side One Select line defines which side of a two sided disc is used for information
transfer.
A high logic level selects the side' '0" read/write head and a low logic level selects the side 1
read/write head.
Output Status Lines
Index
An index pulse occurs once every revolution of the disc (200 msec. nominal) to indicate the
begining of a track.
The leading edge of this signal is used to insure data accuracy during format. The index line
remains low for the duration of the index pulse.
Track 0
This line indicates to the controller that the read/write head is positioned on track O. The
track
a
signal remains low until the head is moved from track O. This is accomplished by
anding the track
a
switch and phase
a
of the stepper motor control.
Write Protected
This line goes low when the disc is write protected to disable the write electronics.
When the write protect line goes high, the write electronics are enabled and write operations
may be performed. If the controller issues a write command when the disc is write protected
an error condition will be reported to the host system.
Composite Read Data
Data and clock transitions are transmitted on this line when the disc drive is selected. Each
flux transition detected by the head provides a logic low pulse of 1 J-lsec.
±.
25 on this line.