8-Port interrupt generation logic

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The asynch adapter implements eight system interrupt request lines.

The adapter implements the following eight system interrupt request lines:

  • IRQ 3
  • IRQ 5
  • IRQ 9
  • IRQ 10
  • IRQ 11
  • IRQ 12
  • IRQ 14
  • IRQ 15

Only one request line is active during normal operation. All 8-port adapters in one system should use the same interrupt level for optimal system performance. The active line is selected by writing to the appropriate POS register during the setup cycle. The adapter supports interrupt sharing and implements an open collector configuration. In this arrangement, the interrupt line is pulled high by a system pull-up resistor. The adapter pulls the line low to indicate an active interrupt request.