Ziatech Corporation ZT 8809A, Руководство по эксплуатации

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ZT 88CT08A/88CT09A CMOS Boards
If the processor must operate at slow processor speed 100% of the
time, hardware jumper W46A may select this, leaving the SLIN* bit
free for printer use. The board is shipped from the factory with both
W46A and W46B removed, selecting full processor speed and leaving
SLIN* free for printer use.
You may not use this feature with STD DOS, which is a time-
dependent application. The Systick Timer will continue to interrupt
DOS each 55 milliseconds; the processor, running at an extremely
slow speed, would consequently spend almost all its processing time
servicing this interrupt. This is only one reason why STD DOS does
not allow this feature. We recommend that you not use this feature
with STD DOS on the ZT 88CT08A and ZT 88CT09A.
Halt With Restart Via Interrupt
To further decrease power consumption from the Clock Slowdown
mode described above, you may halt the processor clock during times
processing is not needed and restart it by an interrupt. This interrupt
may be from an external source, such as an event requiring service
from the processor, or from one of the on-board timers. Since the
three 16-bit timers from the 8254 are driven by an independent
oscillator, the timers continue to run at their full 1.19 MHz frequency
and are not affected by a stopped processor clock. Alternatively, the
timer clock inputs could count external events and interrupt the
processor upon reaching a predetermined count. Any counters not
initialized remain idle and do not affect power consumption.
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