Indirectly Supported Internal Interrupt Sources - Intel 80C188EC User Manual

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INTERRUPT CONTROL UNIT

Indirectly Supported Internal Interrupt Sources

The interrupt request lines for DMA channel 0 and DMA channel 1 and the receive and transmit

interrupts for serial channel 1 are not tied internally to the Interrupt Control Unit. These interrupt

requests are routed to external device pins through the Port 3 multiplexer (Figure 8-23). If a sys-

tem requires interrupt support for these devices, the multiplexed interrupt request outputs must

be externally connected to the INT input pins of the Interrupt Control Unit.

DMA Channel 2

DMA Channel 3

Serial Channel 0 Receive

Serial Channel 0 Transmit

Figure 8-22. Default Slave 8259 Module Priority

Highest Priority

Lowest Priority