M38B78F7H-XXXXFP View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

Manufacturer

M38B78F7H-XXXXFP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

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INTERRUPTS

Interrupts occur by twenty two sources: five external, sixteen inter-

nal, and one software.

Interrupt Control

Each interrupt except the BRK instruction interrupt has both an inter-

rupt request bit and an interrupt enable bit, and is controlled by the

interrupt disable flag. An interrupt occurs if the corresponding inter-

rupt request and enable bits 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 soft-

ware. The BRK instruction interrupt and reset cannot be disabled

with any flag or bit. The I flag disables all interrupts except the BRK

instruction interrupt and reset. If several interrupts requests occur at

the same time, the interrupt with highest priority is accepted first.

Interrupt Operation

Upon acceptance of an interrupt the following operations are auto-

matically performed:

1. The contents of the program counter and 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.

Interrupt Source Selection

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

rupt source switch register (address 003916).

1. INT1 or Serial I/O3

2. INT3 or Serial I/O2 transmit

3. INT4 or A-D conversion

sNote

When the active edge of an external interrupt (INT0–INT4) is set or

when switching interrupt sources in the same vector address, the

corresponding interrupt request bit may also be set. Therefore, please

take following sequence:

(1) Disable the external interrupt which is selected.

(2) Change the active edge in interrupt edge selection register

(3) Clear the set interrupt request bit to “0.”

(4) Enable the external interrupt which is selected.

MITSUBISHI MICROCOMPUTERS

38B7 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

20

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