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8259A PRIORITY INTERRUPT CONTROLLER

Jan 04, 2016

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8259A PRIORITY INTERRUPT CONTROLLER. 8086 has 2 interrupt inputs 1. NMI 2. INTR - PowerPoint PPT Presentation

8259A PRIORITY INTERRUPT CONTROLLER

8259A PRIORITY INTERRUPT CONTROLLER8086 has 2 interrupt inputs 1. NMI2. INTRFor 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.8259A Overview and system connection

8259A PIC

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Master and slaveMaster The 8259A connected directly into the 8086 INTR pin is called as masterSlave 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

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 needto initialize all of them.iMp8Initializing an 8259AFind the system base addressFind the internal addressSystem address=internal address + base address

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