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TMP92CM22
2007-02-16
92CM22-211
3.12 Watchdog Timer (Runaway detection timer)
The TMP92CM22 contains a watchdog timer of runaway detecting.
The watchdog timer (WDT) is used to return the CPU to the 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 INTWD to notify the CPU of
the malfunction.
Connecting the watchdog timer output to the reset pin internally forces a reset.
(The level of external
RESET
pin is not changed.)
3.12.1 Configuration
Figure 3.12.1 is a block diagram of the watchdog timer (WDT).
Figure 3.12.1 Block Diagram of Watchdog Timer
Note: Care must be exercised in the overall design of the apparatus since the watchdog timer may fail
to function correctly due to external noise, etc.
WDMOD
<WDTE>
RESET pin
Selector
2
15
2
17
2
19
2
21
Binary counter
(22-Stage)
Q
R S
Watchdog timer register
control register WDCR
Write
B1H
Write
4EH
Reset
control
WDMOD<RESCR>
Internal reset
Interrupt
request
INTWD
Internal reset
f
IO
WDMOD
<WDTP1:0>
Internal data bus
Reset