timers-017
Load register
(WLDR)
Counter register
(WCRR)
0xFFFF FFFF
Overflow
reset pulse is
generated.
Trigger register
(WTGR)
0x0000 0000
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Watchdog Timers
After reset generation, the counter is automatically reloaded with the value stored in the watchdog load
register (WDTi.
) and the prescaler is reset (the prescaler ratio remains unchanged). Then, after the
reset pulse output has been generated, the timer counter begins incrementing again.
shows a general functional view of the WDT.
Figure 16-17. WDT General Functional View
16.4.3.4 Prescaler Value/Timer Reset Frequency
Each WDT is composed of a prescaler stage and a timer counter.
The timer rate is defined by the following values:
•
Value of the prescaler fields (the WDTi.
[5] PRE bit and the WDTi.
[4:2] PTV field)
•
Value loaded into the timer load register (WDTi.
The prescaler stage is clocked with the timer clock and acts as a clock divider for the timer counter stage.
The ratio is managed by accessing the ratio definition field (the WDTi.
[4:2] PTV field) and is
enabled with the WDTi.
[5] PRE bit.
lists the prescaler clock ratio values.
Table 16-63. Prescaler Clock Ratios
PRE Bit (in WDTi.
Register)
PTV Bits (in WDTi.
Register)
Clock Divider (PS)
0
X
1
1
0
1
1
1
2
1
2
4
1
3
8
1
4
16
1
5
32
1
6
64
1
7
128
2751
SWPU177N – December 2009 – Revised November 2010
Timers
Copyright © 2009–2010, Texas Instruments Incorporated