North Star MDS-A-O User Manual page 34

5. If the data write case then
&a issue begin write command.
ba wait for WI status bit to be false.
Ca write
15/31
bytes of zeros
a
d. write the sync character (s) (FB hex).
e. write 256/512 bytes of data from RAM while computing the
cyclic check character.
fa write the check character.
ga if more blocks to write on the same track then wait until
the next sector pulse and repeat from step a, otherwise
donea
6. If read case then
aa wait for RE to be true and test DD status bit.
ba wait for sync character detection {i.ea body model
a
Report
an error if the sync character is not detected
a
c. read 256/512 data bytes into RAM while computing the check
cbaractera
d. r.ad the check character and compare with the computed
check character. Report an error if they are not equal.
e. if there are more blocks to read on the same track then
. .it 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 c data bytes read from the disk should be
caepared for equality with the data in RAM. Report an error
if corresponding bytes do not compare.
DISK CONTROLLER INTERRUPTS
The software provided with the disk system is not interrupt
drivena The controller can cause an interrupt on anyone of the
interrupt lines on the 5-190 bus
by
connecting the appropriate
jumper
at
the lower left corner of the controller board. An
int.rrupt will be generated at every sector pulse while the
interrupt is armed in the controller
a
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 interrupta
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.
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North Star, MICRO-DISK System
34