Hardware manual

Microcomputer Technical Q&A
28
Q&A No.: QAH8S-024
Category: Interrupts
Subject: Use of IRQ Status Register
Question
The IRQ status register (ISR) can be cleared to 0 by the user. When is this register used?
Answer
The IRQ status register is cleared to 0 automatically. Therefore, the user consciously clears this
register in the following cases:
• In level sensing
• If there is a risk of generation of an unwanted interrupt before interrupts are enabled (e.g.
during initialization or when pin connections are changed), total clearing can be performed
directly before enabling interrupts
• When IRQ status register bits are used as flags, without enabling interrupts
• When multiplication interrupts are generated, to execute only high-priority processing, and not
low-priority processing
Applicable Products
Applicability Series Applicability Series Applicability Series
Yes Entire H8S Series H8S/2655 H8S/2350
H8S/2355 H8S/2357 H8S/2345
H8S/2245 H8S/2148 H8S/2144
H8S/2138 H8S/2134 H8S/2128
H8S/2124 — — — —