Specifications

Programming the VMEbus Interface
5
5
5-9
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.
• Upon returning from the interrupt handling routine, go back to the beginning of
the loop until no more interrupts are active. In other words, you must handle all
other active interrupts. This includes all other interrupts and errors which come
in prior to calling the interrupt handling routine as well as any new interrupts and
errors which may occur during this process. Only when all interrupts and error
conditions are handled may you return from the overall interrupt handler. Again,
if you miss any interrupts or errors, no other interrupts or errors will be
recognized.
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