M38503M4H Datasheet, PDF (17/51 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3850 Group (Spec. H)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
INTERRUPTS
Interrupts occur by 14 sources among 14 sources: six external,
seven internal, and one software.
Interrupt Control
Each interrupt is controlled by an interrupt request bit, an interrupt
enable bit, and the interrupt disable flag except for the software in-
terrupt set by the BRK instruction. An interrupt occurs if the
corresponding interrupt request and enable bits are “1” and the in-
terrupt disable flag is “0”.
Interrupt enable bits can be set or cleared by software.
Interrupt request bits can be cleared by software, but cannot be
set by software.
The BRK instruction cannot be disabled with any flag or bit. The I
(interrupt disable) flag disables all interrupts except the BRK in-
struction interrupt.
When several interrupts occur at the same time, the interrupts are
received according to priority.
Interrupt Operation
By acceptance of an interrupt, the following operations are auto-
matically performed:
1. The contents of the program counter and the processor status
register are automatically pushed onto the stack.
2. The interrupt disable flag is set and the corresponding interrupt
request bit is cleared.
3. The interrupt jump destination address is read from the vector
table into the program counter.
sNotes
When the active edge of an external interrupt (INT0–INT3, CNTR0,
CNTR1) is set, the corresponding interrupt request bit may also be
set. Therefore, take the following sequence:
1. Disable the interrupt
2. Change the interrupt edge selection register
(the timer XY mode register for CNTR0 and CNTR1)
3. Clear the interrupt request bit to “0”
4. Accept the interrupt.
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