Timing Considerations
Usually all that is needed to utilize the timing part of the modem controller
is access to a time reference. For example, the number of milliseconds since
power-up or program launch, or a system tick value can be used.
Under DOS, the INT 1C timer tick produces an interrupt every 55 ms. An Interrupt
Service Request (ISR) can be installed on this interrupt to add 55 to a
long integer every time it is called. This provides a millisecond counter.
On the Macintosh, the Tick Count function returns the number of vertical-retrace
ticks since computer power-up. Each tick represents 1/60 of a second.
Click on one of the following topics for more information:
Programming for Time
When to Consider Time
Recovering when Out of Sync
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