Introduction; Vmechip2 Tick Timer 1 Periodic Interrupt Example - Motorola MVME172 Programmer's Reference Manual

Introduction

This appendix demonstrates how to use interrupts on the MVME172. It
gives an example of how to generate and handle a VMEchip2 Tick Timer
1 interrupt on an MVME172 that has a VMEbus connection. Specific
values have been given for the register writes.
Read this entire appendix before performing any of these procedures.
VMEchip2 Tick Timer 1 Periodic Interrupt
Example
BUsing Interrupts on
1.
Set up Tick Timer:
Step Register and Address
1 Prescaler
Control Register
$FFF4004C
2 Tick Timer 1
Compare Register
$FFF40050
3 Tick Timer 1
Counter Register
$FFF40054
the MVME172
Action and Reference
If not already initialized by the
debugger, initialize as follows:
Prescaler Register = 256 - Bclock
(MHz). This gives a 1 MHz clock
to the tick timers. Bclock is the
bus clock rate, such as 25 MHz.
256 - 25 = $E7.
For periodic interrupts, set the
Compare Register value = Period
(s). For example, if you want an
interrupt every millisecond, set
the register value to 1000 ($3E8).
Refer to the Tick Timer 1
Compare Register
Chapter 2.
Write a zero to clear.
B
description in
B-1