HD64F3039F18 Datasheet, PDF (134/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 5 Interrupt Controller
Either of the methods shown below should be used to prevent this problem.
Method 1: When clearing the IRQaF flag, read ISR as a byte unit instead of using a bit-
manipulation instruction, and write a byte value that clears the IRQaF flag to 0 and sets the other
bits to 1.
Example: When a = 0
MOV.B @ISR, R0L
MOV.B #HFE, R0L
MOV.B R0L, @ISR
Method 2: Perform dummy processing within the IRQb interrupt exception handling routine to
clear the IRQbF flag.
Example: When b = 1
IRQB MOV.B #HFD, R0L
MOV.B R0L, @ISR
Rev.3.00 Mar. 26, 2007 Page 110 of 682
REJ09B0353-0300