Specifications

EPC-5A Hardware & Software Reference Manual

Page 84

Start of Loop

• Determine the source of the interrupt or event. This can be done by reading the

VME Interrupt State register which should be ANDed with the VME Interrupt

Enable register. As described above, the VME Event State register and VME

Event enable register may also be potential sources for the generation of IRQ10.

Keep in mind that all pending interrupts must be handled.

• If the interrupt is a VMEbus interrupt 1-7;

Acknowledge the interrupt to the VMEbus device generating the interrupt as

follows:

1. Set the IACK bit in the VME Modifier register

2. Establish a byte-ordering for the status/ID to be read. Whether this is an

8-bit or 16-bit read is dependent on the card issuing the interrupt

3. The address modifiers and transfer length are dependent on the hardware

generating the interrupt.

4. Perform a read of the VMEbus where the address being read reflects the

interrupt level being responded to. Address lines A3-A1 must reflect the

interrupt level in binary form. Multiply the interrupt level by 2 and use

that as the address of the read operation.

5. After the read operation, clear the IACK bit in the VME Modifier register.

•

If the interrupt is a VXIbus message interrupt, the interrupt is acknowledged and

cleared by reading the appropriate register(s), followed by setting the WRDY bit

in the VME Response register.

•

Call your interrupt handling routine.