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80C186EC/80C188EC Microprocessor User's Manual

80C186EC/80C188EC Microprocessor User's Manual

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INTERRUPT CONTROL UNIT<br />

Internal<br />

Interrupt<br />

Request<br />

Clear Internal<br />

Request (From<br />

IRL Control Logic)<br />

Interrupt Request<br />

Latch Bit<br />

SET<br />

CLEAR<br />

Q<br />

To 8259A Module<br />

or Port MUX<br />

CLKOUT<br />

Internal<br />

Interrupt<br />

Request<br />

Output of<br />

Interrupt<br />

Request<br />

Latch<br />

A1230-0A<br />

Figure 8-21. Interrupt Request Latch Register Function<br />

8.5.1.1 Directly Supported Internal Interrupt Sources<br />

Seven of the eleven internal interrupt sources are directly supported by the Interrupt Control Unit.<br />

The connections between the Interrupt Request Latch Registers and the slave 8259A module are<br />

“hardwired” and are not programmable. The default priority (see Figure 8-22) within the slave<br />

8259A module is fixed due to the internal connections. The default priority can be changed by<br />

using Specific or Automatic Rotation.<br />

8-37

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