Hardware manual

Microcomputer Technical Q&A
32
Q&A No.: QAH8S-028
Category: Interrupts
Subject: Simultaneous IRQ Interrupts of the Same Priority
Questions
1. With external interrupts, if interrupts within the group with the same priority (IRQ4 to IRQ7)
are generated simultaneously (e.g. IRQ4 and IRQ7), which has priority?
2. What will happen if an IRQ4 interrupt is generated in the IRQ7 interrupt handling routine? (Is
IRQ4 held pending, or is IRQ4 handling given priority?)
Answers
1. The priority order within the IRQ4 to IRQ7 interrupt group is: IRQ4 > IRQ5 > IRQ6 > IRQ7.
2. The IRQ7 interrupt is accepted first. If interrupts are enabled in the IRQ7 handling routine
immediately after the IRQ7 interrupt is accepted, interrupts IRQ4 to IRQ7 can then be
accepted. If interrupts are not enabled in the IRQ7 handling routine, these interrupts can be
accepted after returning from the IRQ7 handling routine.
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 — — — —