UPD78F1502AGK-GAK-AX Datasheet, PDF (764/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 19 INTERRUPT FUNCTIONS
(1) Interrupt request flag registers (IF0L, IF0H, IF1L, IF1H, IF2L, IF2H)
The interrupt request flags are set to 1 when the corresponding interrupt request is generated or an instruction is
executed. They are cleared to 0 when an instruction is executed upon acknowledgment of an interrupt request or
upon reset signal generation.
When an interrupt is acknowledged, the interrupt request flag is automatically cleared and then the interrupt routine is
entered.
IF0L, IF0H, IF1L, IF1H, IF2L, and IF2H can be set by a 1-bit or 8-bit memory manipulation instruction. When IF0L
and IF0H, IF1L and IF1H, and IF2L and IF2H are combined to form 16-bit registers IF0, IF1, and IF2, they can be set
by a 16-bit memory manipulation instruction.
Reset signal generation clears these registers to 00H.
Cautions 1. When operating a timer, serial interface, or A/D converter after standby release, operate it once
after clearing the interrupt request flag. An interrupt request flag may be set by noise.
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 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.
Remark If an instruction that writes data to this register is executed, the number of instruction execution clocks
increases by 2 clocks.
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Jun 20, 2011