TMP91C824
91C824-189
3.12 Watch Dog Timer (runaway detection timer)
The TMP91C824 features a watch dog timer for detecting runaway.
The watch dog timer (WDT) is used to return the CPU to normal state when it detects that the CPU has started
to malfunction (runaway) due to causes such as noise.
When the watch dog timer detects a malfunction, it generates a non-maskable interrupt INTWD to notify the
CPU. Connecting the watch dog timer output to the Reset pin internally forces a reset.
3.12.1 Configuration
Figure 3.12.1 is a block diagram of he watchdog timer (WDT).
Internal Reset
WDMOD
<WDTP1 to WDTP0>
WDMOD <WDTE>
Reset
WDT Control register WDCR
Q
R
S
Binary Counter
(22 Stage)
2
21
Internal Reset
WDMOD <RESCR>
WDTI interrupt
f
SYS
(f
FPH
/2)
Selector
2
19
2
17
2
15
Internal data bus
Write
B1H
Write
4EH
RESET
Reset Control
Figure 3.12.1 Block diagram of watch dog timer