TMP93CS32F datasheet(149/180 Pages) TOSHIBA

149 / 180 page

TMP93CS32

2004-02-10

93CS32-147

3.11.3

Operation

The watchdog timer generates interrupt INTWD after the detecting time set in the

WDMOD<WDTP1:0>. The watchdog timer must be zero-cleared by software before an

INTWD interrupt is generated. If the CPU malfunctions (Runaway) due to causes such as

noise, but does not execute the instruction used to clear the binary counter, the binary

counter overflows and an INTWD interrupt is generated. The CPU detects malfunction

(Runaway) due to the INTWD Interrupt and it is possible to return to normal operation by

an anti-mulfunction program. By connecting the watchdog timer out pin to peripheral

devices’ resets, a CPU malfunction can also be acknowledged to other devices.

The watchdog timer restarts operation immediately after resetting is released.

The watchdog timer stops its operation in the IDLE1 and STOP modes. In the RUN and

IDLE2 modes, the watchdog timer is enabled.

However, the function can be disabled when entering the RUN, IDLE2 mode.

Example:

1. Clear the binary counter.

WDCR

← 0 1 0 0 1 1 1 0

Write clear code (4EH).

2. Set the watchdog timer detecting time to 2

17/fSYS.

WDMOD

← 1 0 1 −− − XX

3. Disable the watchdog timer.

WDMOD

← 0 − − − − − X X

Clear WDTE to “0”.

WDCR

← 1 0 1 1 0 0 0 1

Write disable code (B1H).

4. Set IDLE1 mode.

WDMOD

← 0 − − − 10 X X

WDCR

← 1 0 1 1 0 0 0 1

Disables WDT and sets IDLE1 mode.

Executes HALT command.

Set the HALT mode.

5. Set the STOP mode (Warm-up time: 2

16/fSYS).

WDMOD

←− − − 1 0 1 X X

Set the STOP mode.

Executes HALT command.

Set the HALT mode.

X: Don’t care

−: No change

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