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CHAPTER 8
INTERRUPT CONTROL UNIT
8.1
FUNCTIONAL OVERVIEW............................................................................................ 8-1
8.2
MASTER MODE ............................................................................................................ 8-2
8.2.1
Generic Functions in Master Mode ...........................................................................8-2
8.2.1.1
Interrupt Masking .............................................................................................8-3
8.2.1.2
Interrupt Priority ...............................................................................................8-3
8.2.1.3
Interrupt Nesting ..............................................................................................8-4
8.3
FUNCTIONAL OPERATION IN MASTER MODE ......................................................... 8-5
8.3.1
Typical Interrupt Sequence .......................................................................................8-5
8.3.2
Priority Resolution .....................................................................................................8-5
8.3.2.1
Priority Resolution Example ............................................................................8-6
8.3.2.2
Interrupts That Share a Single Source ............................................................8-7
8.3.3
Cascading with External 8259As ..............................................................................8-7
8.3.3.1
Special Fully Nested Mode ..............................................................................8-8
8.3.4
Interrupt Acknowledge Sequence .............................................................................8-9
8.3.5
Polling .......................................................................................................................8-9
8.3.6
Edge and Level Triggering ......................................................................................8-10
8.3.7
Additional Latency and Response Time .................................................................8-10
8.4
PROGRAMMING THE INTERRUPT CONTROL UNIT ............................................... 8-11
8.4.1
Interrupt Control Registers ......................................................................................8-12
8.4.2
Interrupt Request Register ......................................................................................8-16
8.4.3
Interrupt Mask Register ...........................................................................................8-16
8.4.4
Priority Mask Register .............................................................................................8-17
8.4.5
In-Service Register .................................................................................................8-18
8.4.6
Poll and Poll Status Registers .................................................................................8-19
8.4.7
End-of-Interrupt (EOI) Register ...............................................................................8-21
8.4.8
Interrupt Status Register .........................................................................................8-22
8.5
SLAVE MODE ............................................................................................................. 8-23
8.5.1
Slave Mode Programming ......................................................................................8-25
8.5.1.1
Interrupt Vector Register ...............................................................................8-26
8.5.1.2
End-Of-Interrupt Register ..............................................................................8-27
8.5.1.3
Other Registers .............................................................................................8-28
8.5.2
Interrupt Vectoring in Slave Mode ...........................................................................8-29
8.5.3
Initializing the Interrupt Control Unit for Master Mode .............................................8-30
CHAPTER 9
TIMER/COUNTER UNIT
9.1
FUNCTIONAL OVERVIEW............................................................................................ 9-1
9.2
PROGRAMMING THE TIMER/COUNTER UNIT .......................................................... 9-6
9.2.1
Initialization Sequence ............................................................................................9-11
9.2.2
Clock Sources .........................................................................................................9-12
9.2.3
Counting Modes ......................................................................................................9-12
9.2.3.1
Retriggering ...................................................................................................9-13
CONTENTS
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