M34280E1FP View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

Manufacturer

M34280E1FP

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTERS

MITSUBISHI ELECTRIC  

MITSUBISHI MICROCOMPUTERS

4280 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTERS

WATCHDOG TIMER

Watchdog timer provides a method to reset and restart the system

when a program runs wild. Watchdog timer consists of 14-bit

timer (WDT) and watchdog timer flags (WDF1, WDF2).

Watchdog timer downcounts the instruction clock (INSTCK) as

the count source. When the timer WDT count value becomes

000016 and underflow occurs, the WDF1 flag is set to “1.” Then,

when the WRST instruction is not executed before the timer WDT

counts 16383, WDF2 flag is set to “1” and internal reset signal is

generated and system reset is performed.

When using the watchdog timer, execute the WRST instruction

at period of 16383 machine cycle or less to keep the

microcomputer operation normal.

Timer WDT is also used for generation of oscillation stabilization

time. When system is returned from reset and from RAM back-

up mode by key-input, software starts after the stabilization

oscillation time until timer WDT downcounts to 3E0016 elapses.

Software

start

Software

start

3FFF16

3E0016

Value of timer WDT

0000 16

WDF1 flag “1”

“0”

WDF2 flag “1”

“0”

“H”

Internal reset signal “L”

System reset

POF

instruction

execution

Return

WRST

instruction

execution

Fig. 14 Watchdog timer function

Software

start

System reset

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ELECTRIC

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