MOTOROLA
TIMER/RESET MODULE
MMC2001
9-8
REFERENCE MANUAL
Figure 9-8 TOD Fraction Alarm Register
9.5 Watchdog Timer
The watchdog timer is used to protect against system failures by providing a means
of escape from unexpected events or programming errors. Once started, the watch-
dog timer must be serviced by software on a periodic basis. If servicing does not take
place, the watchdog times out and asserts a reset signal.
Figure 9-9 Watchdog Timer Block Diagram
TODFAR — TOD Fraction Alarm Register
10001014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
TOD FRACTION ALARM REGISTER
0
0
0
0
0
0
0
0
W
RESET:
Undefined on POR
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
RESET:
(From Clock Block)
Reset
WDE (one-time write)
DBUG (from CPU)*
WDBG (one-time write)
Watchdog Control Register (WCR)
6-Bit Counter
Underflow
Watchdog Service Register (WSR)
WS
TP
WDBG
WDE
STOP (from CPU)*
WSTP (one-time write)
DOZE (from CPU)*
WDZE (one-time write)
WDZE
2 Hz
* NOTE: DOZE and STOP are generated from the CPU signals LPMD1 and LPMD0
DBUG is an active high signal from the CPU indicating debug mode
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