RL78/G15 CHAPTER 14 INTERRUPT FUNCTIONS
R01UH0959EJ0110 Rev.1.10 Page 608 of 765
Mar 7, 2023
Caution 2. When manipulating a flag of the interrupt request flag register, use a 1-bit memory manipulation
instruction (CLR1). When describing in C language, use a bit manipulation instruction such as
“IF0L.0 = 0;” or “_asm(“clr1 IF0L.0”);” because the compiled assembler must be a 1-bit memory
manipulation instruction (CLR1).
If a program is described in C language using an 8-bit memory manipulation instruction such as
“IF0L &= 0xfe;” and compiled, it becomes the assembler of three instructions.
mov a, IF0L
and a, #0FEH
mov IF0L, a
In this case, even if the request flag of the another bit of the same interrupt request flag register
(IF0L) is set to 1 at the timing between “mov a, IF0L” and “mov IF0L, a”, the flag is cleared to 0 at
“mov IF0L, a”. Therefore, care must be exercised when using an 8-bit memory manipulation
instruction in C language.
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