Motorola MVME172 用户手册
B
B-1
B
Using Interrupts on
the MVME172
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.
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
Example
1.
Set up Tick Timer:
Step
Register and Address
Action and Reference
1
Prescaler
Control Register
$FFF4004C
Control Register
$FFF4004C
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.
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.
2
Tick Timer 1
Compare Register
$FFF40050
Compare Register
$FFF40050
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
Compare Register value = Period
(s). For example, if you want an
interrupt every millisecond, set
the register value to 1000 ($3E8).
Refer to the
description in
Chapter 2.
3
Tick Timer 1
Counter Register
$FFF40054
Counter Register
$FFF40054
Write a zero to clear.