Watchdog Timer (Wdt); Watchdog Timer Configuration - Philips CEM2100/00 Service Manual

6. Watchdog Timer (WDT)

The watchdog timer is a fail-safe system to detect rapidly the CPU malfunctions such as endless loops due to spu-
rious noises or the deadlock conditions, and return the CPU to a system recovery routine.
The watchdog timer signal for detecting malfunctions can be programmed only once as "reset request" or "inter-
rupt request". Upon the reset release, this signal is initialized to "reset request".
When the watchdog timer is not used to detect malfunctions, it can be used as the timer to provide a periodic inter-
rupt.
Note: Care must be taken in system design since the watchdog timer functions are not be operated completely due to
effect of disturbing noise.

6.1 Watchdog Timer Configuration

23 15
fc/2 or fs/2
21 13
fc/2 or fs/2
19 11
fc/2 or fs/2
17 9
fc/2 or fs/2
Internal reset
WDTT
Binary counters
Clock
1 2
Clear
2
Q
S R
WDTEN
Writing
disable code
Controller
0034 0035
H H
WDTCR1 WDTCR2
Watchdog timer control registers
Figure 6-1 Watchdog Timer Configuration
Reset release
Overflow WDT output
Writing
WDTOUT
clear code
Page 65
T5CL8
R
Reset
S
Q
request
Interrupt request
INTWDT
interrupt
request