SIGNALS WHEN DRIVING A DISK
The following describes the interface under driver control.
SEL1B-, SEL2B-, SEL3B-
Select lines for the three external disk drives active low.
TK
A selected drive pulls this signal low whenever its read-write head
is on track 00.
RDY-
When a disk drive's motor is on, this line indicates the selected
disk is installed and rotating at speed. The driver ignores this signal.
When the motor is off this is used as a ID data line. See below.
WPRO- (Pin #14)
A selected drive pulls this signal low whenever it has a write-
protected diskette installed.
INDEX- (Pin #22)
A selected drive pulses this signal low once for each revolution of
its motor.
SIDEB- (Pin #13)
The system drives this signal to all disk drives-low for side 1, high
for side 0.
STEPB- (Pin #18)
Pulsed to step the selected drive's head.
DIRB (Pin #19)
The system drives this signal high or low to tell the selected drive
which way to step when the STEPB- pulse arrives. Low means step in (to
higher-numbered track); high means step out.
DKRD- (Pin #2)
A selected drive will put out read data on this line.
DKWDB- (Pin #17)
The system drives write data to all disks via this signal. The data
is only written when DKWEB- is active (low). Data is written only to
selected drives.
- Appendix I 355 -
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