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CHAPTER 2 CPU
2.8.2 Interrupt Control Register (ICR)

The interrupt control register, which is provided in the interrupt controller, is used to

set the level for each interrupt request. The ICR is divided to correspond to individual

interrupt causes. The ICR is mapped in the I/O address space and accessed from the

CPU via the bus.

Configuration of Interrupt Control Register (ICR)
The configuration of the interrupt control register (ICR) is show n below:
Bit Functions of Interrupt Control Register (ICR)
[bit 4] ICR4
This bit is always 1.
[bit 3 to 0] ICR3 to 0
These four bits correspond to the four low-order bits of the interrupt level o f the
corresponding interrupt cause. The bits can be read and writte n.
The bits together with bit 4 enable the ICR to specify a value in t he range from 16 to 31.
Interrupt Control Register (ICR) Mapping
Table 2.8.2 Assignments of interrupt causes and interrupt vector s
See Chapter 8, "Interrupt Controller," for more information.
76543210
ICR4 ICR3 ICR2 ICR1 ICR0 ---11111
R R/W R/W R/W R/W
Initial value
Table 2.8-2 Assignments of Interrupt Causes and Interrupt Vectors
Interrupt
cause Interrupt control register Corresponding interrupt vector
Number Address Number Address
Hexadecimal Decimal
IRQ00 ICR00 0000040 0H10H16 TBR+3BCH
IRQ01 ICR01 0000040 1H11H17 TBR+3B8H
IRQ02 ICR02 0000040 2H12H18 TBR+3B4H
:
::
::
::
::
::
:
IRQ45 ICR45 0000042DH3DH61 TBR+308H
IRQ46 ICR46 0000042EH3EH62 TBR+304H
IRQ47 ICR47 0000042FH3FH63 TBR+300H