8-29
INTERRUPT CONTROL UNIT
8.5.2 Interrupt Vectoring in Slave Mode
In Slave mode, the external 8259A module acts as the master interrupt controller. Therefore, in-
terrupt acknowledge cycles are required for every interrupt, including those from integrated pe-
ripherals. During the first interrupt acknowledge cycle, the external 8259A determines which
slave interrupt controller has the highest priority interrupt request. It then drives that slave’s ad-
dress onto its CAS2:0 pins (Figure 8-20). External logic must decode the correct slave address
from the CAS2:0 pins to drive the SELECT pin.
Figure 8-20. Interrupt Vectoring in Slave Mode
The SELECT pin is the slave-select input to the Interrupt Control Unit. During the second inter-
rupt acknowledge cycle, the highest-priority slave interrupt controller transfers the interrupt type
of its highest priority interrupt to the CPU. If the Interrupt Control Unit is the highest-priority
slave, it passes the interrupt type to the CPU internally; however, the interrupt acknowledge cycle
still must occur for the benefit of the external 8259A module.
T1
T2
T3
T4
CLKOUT
TI
TI
T1
T2
T3
LOCK
CAS2:0
S2:0
INTA0
SELECT
NOTES:
1. INT1/SELECT has the SELECT function in slave mode.
2. INT2/INTA0 has the INTA0 function in slave mode.
3. Cascade address is driven by the external 8259A.
4. SELECT must be driven before phase 2 of T2 of the second INTA.
5. SELECT read by processor.
6. ALE is generated for each INTA.
7. RD is inactive.
Slave Cascade Address From 8259A
T4
INTA
INTA
A1199-A0
Содержание 80C186EA
Страница 1: ...80C186EA 80C188EA Microprocessor User s Manual...
Страница 2: ...80C186EA 80C188EA Microprocessor User s Manual 1995...
Страница 19: ......
Страница 20: ...1 Introduction...
Страница 21: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
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Страница 130: ...4 Peripheral Control Block...
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Страница 139: ......
Страница 140: ...5 ClockGenerationand Power Management...
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Страница 165: ......
Страница 166: ...6 Chip Select Unit...
Страница 167: ......
Страница 190: ...7 Refresh Control Unit...
Страница 191: ......
Страница 205: ......
Страница 206: ...8 Interrupt Control Unit...
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Страница 239: ...INTERRUPT CONTROL UNIT 8 32...
Страница 240: ...9 Timer Counter Unit...
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Страница 265: ......
Страница 266: ...10 Direct Memory Access Unit...
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Страница 295: ...DIRECT MEMORY ACCESS UNIT 10 28...
Страница 296: ...11 Math Coprocessing...
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Страница 314: ...12 ONCE Mode...
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Страница 318: ...A 80C186 Instruction Set Additions and Extensions...
Страница 319: ......
Страница 330: ...B Input Synchronization...
Страница 331: ......
Страница 334: ...C Instruction Set Descriptions...
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Страница 383: ...INSTRUCTION SET DESCRIPTIONS C 48...
Страница 384: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 408: ...Index...
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