Table of Contents
Advertisement
the desired sector position by reading B-status.
If not then
repeat this step.
5. If the data write case then
a. issue start write command.
b. wait for write status bit.
c. write 15 bytes of zeros.
d. write the sync character (FB hex).
e. write 256 bytes of data from RAM while computing the cyclic
check character.
f. write the check character.
g. if more blocks to write on the same track then wait until
the next sector pulse and repeat from step a, otherwise
done.
6. If read case then
a. wait for sync char detection (i.e. body mode). Report an
error if the sync character is not detected within 16 byte
times.
b. read 256 data bytes into RAM while computing the check
character.
c. read the check character and compare with the computed
check character.
Report an error if they are not equal.
d. if there are more blocks to read on the same track then
wait until the next sector pulse and repeat from step a,
otherwise done.
7. If verify case then all is the same as the read case except
that in step b data bytes read from the disk should be
compared for equality with the data in RAM.
Report an error
if corresponding bytes do not compare.
INTERRUPTS
The software provided with the MICRO-DISK System is not
interrupt driven.
The controller can cause an interrupt on any
one of the interrupt lines on the 8-100 bus by connecting the
appropriate jumper at the lower left corner of the controller
board.
An interrupt will be generated at every sector pulse
while the interrupt is armed in the controller.
See the COMMANDS
section for details of interrupt arming and disarming.
Special
user generated, interrupt driven software can be written which
uses the controller sector pulse interrupt.
Before the low level controller software is called,
interrupts should be disabled.
If an interrupt occurs during
data transmission then data can be lost as a result of excessive
delay in the interrupt routine.
North Star MICRO-DISK System
14
Advertisement
Table of Contents
