M16C6S_09 Datasheet, PDF (65/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Interrupts
(5) Modifying Interrupt Control Register
• Each interrupt control register can only be modified while no interrupt requests corresponding to that
register are generated. If interrupt requests managed by any interrupt control register are likely to occur,
disable the interrupts before modifying the register. A sample program is shown below.
To modify any interrupt control register after disabling interrupts, be careful with the instructions used.
Modifying other than the IR bit
If an interrupt request corresponding to that register is generated while executing the instruction, the IR
bit may not be set to “1” (= interrupt requested), with the result that the interrupt request is ignored. If this
presents a problem, use the following instructions to modify the register.
Instructions to use: AND, OR, BCLR, BSET
Modifying the IR bit
Even when the IR bit is cleared to “0” (= interrupt not requested), it may not actually be cleared to “0”
depending on the instruction used. Therefore, use the MOV instruction to clear the IR bit.
Rev.5.01 Dec 10, 2009 page 65 of 201
REJ03B0014-0501