M3885 datasheet(21/103 Pages) RENESAS

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3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

INTERRUPTS

Interrupts occur by 16 sources among 22 sources: thirteen exter-

nal, nine 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 caused by the BRK instruction. An interrupt occurs when

both the corresponding interrupt request bit and interrupt enable

bit are “1” and the interrupt 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 interrupt cannot be disabled with any flag or

bit. The I (interrupt disable) flag disables all interrupts except the

BRK instruction interrupt.

When several interrupts occur at the same time, the interrupts are

serviced according to the 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

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 and stored into the program counter.

Interrupt Source Selection

Any of the following interrupt sources can be selected by the inter-

rupt source selection register (INTSEL).

1. INT0 or Input buffer full

2. INT1 or Output buffer empty

3. Serial I/O receive or LRESET

4. Serial I/O transmission or SCLSDA

5. Timer 2 or INT5

6. CNTR0 or INT0

7. CNTR1 or INT1

8. A-D conversion or Key-on wake-up

External Interrupt Pin Selection

The external interrupt sources of INT2, INT3, and INT4 can be se-

lected from either input pin from INT20, INT30, INT40 or input pin

from INT21, INT31, INT41 by the INT2, INT3, INT4 interrupt switch

bit (bit 4 of PCTL2).

s Notes

When setting the followings, the interrupt request bit may be set to

“1”.

•When setting external interrupt active edge

Related register: Interrupt edge selection register (address

003A16); Timer XY mode register (address

002316)

•When switching interrupt sources of an interrupt vector address

where two or more interrupt sources are allocated

Related register: Interrupt source selection register (address

003916)

•When setting input pin of external interrupts INT2, INT3 and INT4

Related register: INT2, INT3, INT4 interrupt switch bit of Port con-

trol register 2 (bit 4 of address 002F16)

When not requiring the interrupt occurrence synchronized with

these setting, take the following sequence.

➀ Set the corresponding interrupt enable bit to “0” (disabled).

➁ Set the active edge selection bit or the interrupt source selec-

tion bit to “1”.

➂ Set the corresponding interrupt request bit to “0” after 1 or more

instructions have been executed.

➃ Set the corresponding interrupt enable bit to “1” (enabled).

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