M16C6K7 Datasheet, PDF (239/285 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Rev.1.0
Usage precaution
Mitsubishi microcomputers
M16C / 6K7 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
(4) External interrupt
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• When the polarity of the INT0 to INT11 pins is changed, the interrupt request bit is sometimes set to "1".
After changing the polarity, set the interrupt request bit to "0".
(5) Rewrite the interrupt control register
• To rewrite the interrupt control register, do so at a point that does not generate the interrupt request for
that register. If there is possibility of the interrupt request occur, rewrite the interrupt control register after
the interrupt is disabled. The program examples are described as follow:
Example 1:
INT_SWITCH1:
FCLR I
AND.B #00h, 0055h
NOP
NOP
FSET I
; Disable interrupts.
; Clear TA0IC int. priority level and int. request bit.
; Four NOP instructions are required when using HOLD function.
; Enable interrupts.
Example 2:
INT_SWITCH2:
FCLR I
AND.B #00h, 0055h
MOV.W MEM, R0
FSET I
; Disable interrupts.
; Clear TA0IC int. priority level and int. request bit.
; Dummy read.
; Enable interrupts.
Example 3:
INT_SWITCH3:
PUSHC FLG
FCLR I
AND.B #00h, 0055h
POPC FLG
; Push Flag register onto stack
; Disable interrupts.
; Clear TA0IC int. priority level and int. request bit.
; Enable interrupts.
The reason why two NOP instructions (four when using the HOLD function) or dummy read are inserted
before FSET I in Examples 1 and 2 is to prevent the interrupt enable flag I from being set before the
interrupt control register is rewritten due to effects of the instruction queue.
• When a instruction to rewrite the interrupt control register is executed but the interrupt is disabled, the
interrupt request bit is not set sometimes even if the interrupt request for that register has been generated.
This will depend on the instruction. If this creates problems, use the below instructions to change the
register.
Instructions : AND, OR, BCLR, BSET
Noise
(1) Insert the by-pass condencer to the Vcc-Vss line for preventing a noise and latch-up. Connect the by -pass
condencer (about 0.1µF) between Vcc pin and Vss pin. It is distance must be shortest rather sicker line.
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