Programming The Tick Timers; Tick Timer 1 And 2 Compare And Counter Registers - Motorola MVME162FX Programmer's Reference Manual

MC2 Chip

Programming the Tick Timers

3

Tick Timer 1 and 2 Compare and Counter Registers

3-16
There are four programmable tick timers in the MC2 chip. These
timers are identical in function to the timers implemented in the
PCCchip2 and the VMEchip2.
The Tick Timer Counter is compared to the Compare Register.
When they are equal, an interrupt is sent to the local bus interrupter
and the overflow counter is incremented. If the clear on compare
mode is enabled, the counter is also cleared. For periodic interrupts,
the following equation should be used to calculate the compare
register value for a specific period (T).
T (µs) = Compare Register
When programming the tick timer for periodic interrupts, the
counter should be cleared to zero by software and then enabled. If
the counter does not initially start at zero, the time to the first
interrupt may be longer or shorter than expected. The rollover time
for the counter is 71.6 minutes.
The Tick Timer Counter, when enabled, increments every
microsecond. Software may read or write the counter at any time.