tmp86c847iug TOSHIBA Semiconductor CORPORATION, tmp86c847iug Datasheet - Page 66

• Manufacturer Part Number: tmp86c847iug
• Description: 8 Bit Microcontroller
• Manufacturer: TOSHIBA Semiconductor CORPORATION

7.2 Watchdog Timer Control
7. Watchdog Timer (WDT)
7.2 Watchdog Timer Control
7.2.1 Malfunction Detection Methods Using the Watchdog Timer
Example :Setting the watchdog timer detection time to 2
dog timer is automatically enabled after the reset release.
Within 3/4 of WDT
detection time
Within 3/4 of WDT
detection time
The watchdog timer is controlled by the watchdog timer control registers (WDTCR1 and WDTCR2). The watch-
dog timer output is activated by the binary-counter overflow unless the binary counters are cleared. When
WDTCR1<WDTOUT> is set to “1” at this time, the reset request is generated and the
low-level signal, then internal hardware is initialized. When WDTCR1<WDTOUT> is set to “0”, a watchdog
timer interrupt (INTWDT) is generated.
mode, and automatically restarts (continues counting) when the STOP/IDLE/SLEEP mode is inactivated.
The CPU malfunction is detected, as shown below.
If the CPU malfunctions such as endless loops or the deadlock conditions occur for some reason, the watch-
The watchdog timer temporarily stops counting in the STOP mode including the warm-up or IDLE/SLEEP
Note:The watchdog timer consists of an internal divider and a two-stage binary counter. When the clear code 4EH
1. Set the detection time, select the output, and clear the binary counter.
2. Clear the binary counter repeatedly within the specified detection time.
is written, only the binary counter is cleared, but not the internal divider. The minimum binary-counter overflow
time, that depends on the timing at which the clear code (4EH) is written to the WDTCR2 register, may be 3/
4 of the time set in WDTCR1<WDTT>. Therefore, write the clear code using a cycle shorter than 3/4 of the
time set to WDTCR1<WDTT>.
LD
LD
LD
LD
LD
:
:
:
:
(WDTCR2), 4EH
(WDTCR1), 00001101B
(WDTCR2), 4EH
(WDTCR2), 4EH
(WDTCR2), 4EH
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: Clears the binary counters.
: WDTT
: Clears the binary counters (always clears immediately before and
: Clears the binary counters.
: Clears the binary counters.
21
after changing WDTT).
/fc [s], and resetting the CPU malfunction detection
←
10, WDTOUT
←
1
RESET
TMP86C847IUG
pin outputs a