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8259A PRIORITY INTERRUPT CONTROLLER

8259A PRIORITY INTERRUPT CONTROLLER. 8086 has 2 interrupt inputs 1. NMI 2. INTR

anthony-whitaker
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8259A PRIORITY INTERRUPT CONTROLLER

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  1. 8259A PRIORITY INTERRUPT CONTROLLER

  2. 8086 has 2 interrupt inputs 1. NMI 2. INTR • For application where we have interrupts from multiple sources, use an external device called a Priority Interrupt Controller(PIC) to “funnel” the interrupt signals into a single interrupt input on the processor.

  3. 8259A Overview and system connection

  4. 8259A PIC

  5. Master and slave • Master  The 8259A connected directly into the 8086 INTR pin is called as master • Slave The INT pin from the other 8259A connects into an IR input on the master. This secondary or cascaded device is called as a slave

  6. Programming the 8259A • The 8259A is programmed by properly initializing: - 4 ICWs - Initialization command words; - 3 OCWs – Operation command words; • The initialization procedure may not need to initialize all of them.

  7. Initializing an 8259A • Find the system base address • Find the internal address • System address=internal address + base address

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