Hardware manual

Microcomputer Technical Q&A

Q&A No.: QAH8S-029

Category: Interrupts

Subject: Use of Different Interrupt Modes

Question

There are four interrupt control modes. How are these different modes used?

Answer

Modes 0 and 1 are compatible with the H8/300 Series and/or H8/300H Series. Guidelines for

mode selection are given below.

• Mode 0

Controlled by the I bit; useful when multiple interrupts are not used. If multiple interrupts are

not used, the size of the stack, etc., can be limited.

Compatible with the H8/300 Series and H8/300H Series.

• Mode 1

Controlled by the I and UI bits. ICR can be handled easily as longword data, enabling ICR

settings to be made at the start of an interrupt routine.

EXR is not used, enabling the stack size to be limited.

Compatible with the H8/300H Series.

• Mode 2

Enables 8-level multiple interruption to be controlled at high speed.

Note: Interrupt control modes differ from product to product; see the relevant hardware manual

for details.