Using Interrupts on the MVME172

3.Set up an interrupt handler routine:

Step

Action and Reference

 

 

Your interrupt handler should include the following features.

1Be sure the MC68060 vector base register is set up. Set the proper MC68060 exception vector location so the processor vectors to your interrupt handler location. You can determine the proper exception vector location to set from the MC68060 vector base register, the VMEchip2 base register, and Table 2-3, the Local Bus Interrupter Summary, in Chapter 2, from which you can determine the actual interrupt vector given on a Tick Timer 1 interrupt. Lower the MC68060 mask so the interrupt level you programmed is accepted. The interrupt handler itself should include the following (steps 2 through 5).

2Confirm the Tick Timer 1 interrupt occurred, by reading the status of bit 24 of the Interrupter Status Register at $FFF40068. A high indicates an interrupt present.

3Clear Tick Timer 1 interrupt by writing a one to bit 24 of the Interrupt Clear Register at $FFF40074.

4Increment a software counter to keep track of the number of interrupts, if desired. Output a character or some other action (such as toggling the FAIL LED) on an appropriate count, such as 1000.

5Return from exception.

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Motorola manual Using Interrupts on the MVME172