16-Port interrupt generation logic

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The 16-port asynchronous adapter implements eight system interrupt request lines.

The adapter implements the following eight system interrupt request (IRQ) 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 16-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 as defined in the Micro Channel architecture. 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.