Operation During Interrupts

The Scanner Interrupt Management Mode Select (INTM) bit determines scanner priority during an interrupt event.

When INTM = 0 and the MD bits select Burst mode, scanner operation is given higher priority than the interrupt response. This allows the scanner to delay the interrupt response until the scan operation is complete, but at the expense of increased interrupt response time.

When INTM = 0 and the MD bits select Concurrent or Triggered modes, the scanner accesses memory during the interrupt response. Scanner hardware will stall the CPU while the scan operation is in progress. Once the scan is complete, CPU operation resumes, allowing the interrupt response to resume. Interrupt response time is increased by one instruction cycle each time the scanner accesses memory during the interrupt response.

When INTM = 1, the interrupt response is given higher priority than the scanner operation. Scanner operation is delayed until the interrupt response is complete. This allows interrupts to be serviced immediately, but decreases scanner throughput time.

The INTM bit has no effect on scanner or interrupt priority in Peek mode.