Specifications

Interrupt Controller (V40)
Control Logic
This functional block directs the operation of the other ICU blocks
based on the programmed mode of operation. The Control Logic also
interfaces to the CPU for interrupt request and acknowledge signals.
An interrupt request is generated to the CPU if an ICU input has the
correct priority and is not masked. If the CPU interrupts have been
enabled with the "set interrupt" command, it will respond with an
interrupt acknowledge.
Read/Write Control
Logic
The Read/Write Control Logic controls command and data transfer
between the ICU and the CPU. This functional block selects an ICU
register and determines the direction of data travel based on the
address and I/O control inputs.
Initialization and Operation
Registers
The ICU is programmable to provide flexibility in the way interrupts
are handled. The ICU is initialized by writing up to four 8-bit values
called Interrupt Initialization Word 1 through Interrupt Initialization
Word 4. Once initialized, the operation of the ICU is controlled with
three 8-bit values called Interrupt Mask Word, Interrupt Priority and
Finish Word, and Interrupt Mode Word.
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