HD6475348R Datasheet, PDF (119/487 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

then clears the NMI request, so if another interrupt is requested at the NMI pin during the NMI
exception-handling sequence, the NMI exception-handling sequence will be carried out again.
Coding Examples:
To select the rising edge of the NMI input:
To select the falling edge of the NMI input:
BSET.B #4, @H'FEFC
BCLR.B #4, @H'FEFC
IRQ0 (Interrupt Request 0): An IRQ0 interrupt can be requested by a Low input to the IRQ0
pin. A Low IRQ0 input requests an IRQ0 interrupt if the interrupt request enable 0 bit (IRQ0E) in
SYSCR1 is set to 1. IRQ0 must be held Low until the CPU accepts the interrupt. Otherwise the
request will be ignored.
The IRQ0 interrupt can be assigned any priority level from 7 to 0 by setting the corresponding
value in the upper four bits of IPRA. If bit 4 of data transfer enable register A (DTEA) is set to 1,
an IRQ0 interrupt starts the data transfer controller. Otherwise the interrupt is served by the CPU.
In the CPU interrupt-handling sequence for IRQ0, the T bit of the status register is cleared to 0,
and the interrupt mask level is set to the value in the upper four bits of IPRA.
Coding Examples:
To enable IRQ0 to be requested by IRQ0 input:
To assign priority level 7 to IRQ0:
To have IRQ0 start the DTC:
BSET.B #5, @H'FEFC
OR.B #70, @H'FF00
BSET.B #4, @H'FF08
IRQ1 to IRQ5 (Interrupt Request 1 to 5): An IRQ1 to IRQ5 interrupt is requested by a High-to-
Low transition at the IRQ1 to IRQ5 pin. The IRQ1 interrupt is enabled only when the interrupt
request enable 1 bit (IRQ1E) in SYSCR1 is set to 1. IRQ2 to IRQ5 are controlled by bits IRQ2E to
IRQ5E in SYSCR2. (see section 9.7, “Port 6.”)
Interrupts IRQ1 to IRQ5 can be assigned any priority level from 7 (high) to 0 (low) by setting the
corresponding value in IPRA and IPRB. The lower four bits of IPRA determine the priority of
IRQ1. The upper four bits of IPRB determine the priority of IRQ2 and IRQ3. The lower four bits
of IPRB determine the priority of IRQ4 and IRQ5. Interrupt requests IRQ1 to IRQ5 are held in the
interrupt controller and cleared during the corresponding interrupt exception-handling sequence.
Contention among IRQ1 to IRQ5 is resolved when the CPU accepts the interrupt by taking the
interrupt with the highest priority first and holding lower-priority interrupts pending. (Contention
between IRQ2 and IRQ3, or between IRQ4 and IRQ5, is resolved by the priority order shown in
table 5-2.)
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