M30218 Datasheet, PDF (58/467 Pages) Mitsubishi Electric Semiconductor – M30218 Group

IPnrtecrrauupttions _{for Interrupts}
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Precautions for Interrupts
(1) Reading address 0000016
• When maskable interrupt is occurred, CPU read the interrupt information (the interrupt number and
interrupt request level) in the interrupt sequence.
The interrupt request bit of the certain interrupt written in address 0000016 will then be set to “0”.
Reading address 0000016 by software sets enabled highest priority interrupt source request bit to “0”.
Though the interrupt is generated, the interrupt routine may not be executed.
Do not read address 0000016 by software.
(2) Setting the stack pointer
• The value of the stack pointer immediately after reset is initialized to 000016. Accepting an interrupt
before setting a value in the stack pointer may become a factor of runaway. Be sure to set a value in
the stack pointer before accepting an interrupt.
(3) External interrupt
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• Either an “L” level or an “H” level of at least 250 ns width is necessary for the signal input to pins INT0
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through INT5 regardless of the CPU operation clock.
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• When the polarity of the INT0 through INT5 pins is changed, the interrupt request bit is sometimes set to
“1”. After changing the polarity, set the interrupt request bit to “0”. Figure 31 shows the procedure for
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changing the INT interrupt generate factor.
Clear the interrupt enable flag to “0”
(Disable interrupt)
Set the interrupt priority level to level 0
(Disable INTi interrupt)
Set the polarity select bit
Clear the interrupt request bit to “0”
Set the interrupt priority level to level 1 to 7
(Enable the accepting of INTi interrupt request)
Set the interrupt enable flag to “1”
(Enable interrupt)
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Figure 31. Switching condition of INT interrupt request
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