TMP93CS41 datasheet(205/248 Pages) TOSHIBA

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TMP93CS40/TMP93CS41

2004-02-10

93CS40-203

3.13 Watchdog Timer (Runaway Detection Timer) and Warm-up Timer

The TMP93CS40/S41 contains a watchdog timer for runaway detection.

The watchdog timer (WDT) is used to return the CPU to a normal state when it detects that

the CPU has started to malfunction (runaway) due to causes such as noise. When the watchdog

timer detects a malfunction, it generates a non-maskable interrupt to notify the CPU of the

malfunction, and outputs “0” from the watchdog timer out pin WDTOUT to notify peripheral

devices of the malfunction.

Connecting the watchdog timer output to the reset pin internally forces a reset.

The watchdog timer consists of 7-stage and 15-stage binary counters.

These binary counters are also used as a warm-up timer for internal oscillator stabilization.

This is used for releasing stop and also before changing the system clock.

3.13.1

Configuration

Figure 3.13.1 shows the block diagram for the watchdog timer (WDT).

Figure 3.13.1 Block Diagram for Watchdog Timer/Warm-up Timer

÷2 ÷4 ÷8 ÷16

XT1

fc fc/2

fc/8

fc/4

fc/16

SYSCR1<GEAR2:0>

fc/fs changing warm-up clock

SYSCR1<SYSCK>

Selection of WDT and warm-up clock

CPU

7-stage

binary

counter

Selector

15-stage binary counter

WDMOD<WARM>

T45CR<QCU>

SYSCR0<WUEF>

WDTOUT

interrupt control

WDTI interrupt

Enable

RESET

SYSCR0<WUEF>

Reset

WDMOD<RESCR>

Internal reset

WDTOUT

Reset

WDMOD<WDTE>

Write disable

code to WDCR

(B1H)

WDMOD

<WDTP1:0>

Reset

HALT instruction

(STOP, IDLE1 mode)

Write clear code

to WDCR

(4EH)

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