Interrupt Sources; External Interrupt Sources - Renesas H8S/2100 Series Hardware Manual

6-bit single-chip microcomputer

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Interrupt Sources

The interrupt sources of external interrupts are NMI, IRQ15 to IRQ0, KIN15 to KIN0 and WUE15

to WUE0. These interrupts can be used to restore this LSI from software standby mode.

NMI Interrupt

The nonmaskable external interrupt NMI is the highest-priority interrupt, and is always accepted

regardless of the interrupt control mode or the status of the CPU interrupt mask bits. The NMIEG

bit in SYSCR can be used to select whether an interrupt is requested at a rising edge or falling

edge on the NMI pin.

IRQ15 to IRQ0 Interrupts:

Interrupts IRQ15 to IRQ0 are requested by an input signal at pins IRQ15 to IRQ0 or pins

ExIRQ15 to ExIRQ6. Interrupts IRQ15 to IRQ0 have the following features:

• The interrupt exception handling for interrupt requests IRQ15 to IRQ0 can be started at an

independent vector address.

• Using ISCR, it is possible to select whether an interrupt is generated by a low level, falling

edge, rising edge, or both edges, at pins IRQ15 to IRQ0 or pins ExIRQ15 to ExIRQ6.

• Enabling or disabling of interrupt requests IRQ15 to IRQ0 can be selected with IER.

• The status of interrupt requests IRQ15 to IRQ0 is indicated in ISR. ISR flags can be cleared to

0 by software.

When the interrupts are requested while IRQ15 to IRQ0 interrupt requests are generated at low

level of IRQn input, hold the corresponding IRQ input at low level until the interrupt handling

starts. Then put the relevant IRQ input back to high level within the interrupt handling routine and

clear the IRQnF bit (n = 15 to 0) in ISR to 0. If the relevant IRQ input is put back to high level

before the interrupt handling starts, the relevant interrupt may not be executed.

The detection of IRQ15 to IRQ0 interrupts does not depend on whether the relevant pin has been

set for input or output. Therefore, when a pin is used as an external interrupt input pin, clear the

DDR bit of the corresponding port to 0 so it is not used as an I/O pin for another function.

Section 6 Interrupt Controller

Rev. 1.00 May 09, 2008 Page 119 of 954

REJ09B0462-0100