Load register
(WDT_WLDR)
Counter register
(WDT_WCRR)
FFFF FFFFh
Overflow
reset pulse is
generated.
Trigger register
(WDT_WTGR)
0000 0000h
Delay register
(WDT_WDLY)
Delay interrupt is
generated when counter
matches this value
WATCHDOG
20.4.3.4 Reset Context
The watchdog timers are enabled after reset.
lists the default reset values of the two
watchdog timer load registers (the WDT_WLDR) and prescaler ratios (the WDT_WCLR[4:2] PTV bit field).
To get these values, software must read the corresponding WDT_WCLR[4:2] PTV bit field and the 32-bit
register to retrieve the static configuration of the module.
Table 20-102. Count and Prescaler Default Reset Values
Timer
WDT_WLDR Reset Value
PTV Reset Value
WDT
FFFF FFBEh
0
20.4.3.5 Overflow/Reset Generation
When the watchdog timer counter register (WDT_WCRR) overflows, an active-low reset pulse is
generated to the PRCM module. This RESET pulse causes the PRCM module to generate global WARM
reset of the device. It is also driven out of the device through the WD_OUT pin. This pulse is one
prescaled timer clock cycle wide and occurs at the same time as the timer counter overflow.
After reset generation, the counter is automatically reloaded with the value stored in the watchdog load
register (WDT_WLDR) and the prescaler is reset (the prescaler ratio remains unchanged). When the reset
pulse output is generated, the timer counter begins incrementing again.
shows a general functional view of the watchdog timers.
Figure 20-98. Watchdog Timers General Functional View
20.4.3.6 Prescaler Value/Timer Reset Frequency
Each watchdog timer 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 WDT_WCLR[5] PRE bit and the WDT_WCLR[4:2] PTV bit field)
•
Value loaded into the timer load register (WDT_WLDR)
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 WDT_WCLR[4:2] PTV bit field) and is
enabled with the WDT_WCLR[5] PRE bit.
lists the prescaler clock ratio values.
3674Timers
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated