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 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
Страница 229: ......
Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
Страница 255: ......
Страница 283: ......
Страница 284: ...11 Math Coprocessing...
Страница 285: ......
Страница 302: ...12 ONCE Mode...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
Страница 373: ......
Страница 396: ...Index...
Страница 397: ......