82374EB Datasheet, PDF (153/208 Pages) Intel Corporation – SYSTEM COMPONENT (ESC)

82374EB 82374SB
Priority
1
2
3-10
3
4
5
6
7
8
9
10
11
12
13
14
15
Label
IRQ0
IRQ1
IRQ2
IRQ8
IRQ9
IRQ10
IRQ11
IRQ12
IRQ13
IRQ14
IRQ15
IRQ3
IRQ4
IRQ5
IRQ6
IRQ7
Table 24 Typical Interrupt Functions
Controller
Typical Interrupt Source
1
Interval Timer 1 Counter 0 OUT
1
Keyboard
1
Interrupt from Controller 2
2
Real Time Clock
2
Expansion Bus Pin B04
2
Expansion Bus Pin D03
2
Expansion Bus Pin D04
2
Expansion Bus Pin D05
2
Coprocessor Error Chaining
2
Fixed Disk Drive Controller Expansion Bus Pin D07
2
Expansion Bus Pin D06
1
Serial Port 2 Expansion Bus B25
1
Serial Port 1 Expansion Bus B24
1
Parallel Port 2 Expansion Bus B23
1
Diskette Controller Expansion Bus B22
1
Parallel Port 1 Expansion Bus B21
9 1 Interrupt Controller Internal Registers
Several registers are contained internally within each 82C59 The interrupts at the IRQ input lines are handled
by two registers in cascade the Interrupt Request Register (IRR) and the In-Service Register (ISR) The IRR is
used to store all the interrupt levels which are requesting service and the ISR is used to store all the interrupt
levels which are being serviced
Internal circuitry determines the priorities of the bits set in the IRR The highest priority is selected and strobed
into the corresponding bit of the ISR during Interrupt Acknowledge Cycles
The Interrupt Mask Register (IMR) stores the bits which mask the incoming interrupt lines The IMR operates
on the IRR Masking of a higher priority input will not effect the interrupt request lines of lower priority inputs
9 2 Interrupt Sequence
The powerful features of the Interrupt Controller in a microcomputer system are its programmability and the
interrupt routine addressing capability The latter allows direct or indirect jumping to the specific interrupt
routine requested without any polling of the interrupting devices The following shows the interrupt sequence
for an x86 type system (the 8080 mode of the interrupt controller must never be selected when programming
the ESC)
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