Si1000/1/2/3/4/5
Offset = 256 PCA0CPL5 + 256 – PCA0L
Equation 28.5. Watchdog Timer Offset in PCA Clocks
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH5 and
PCA0H. Software may force a WDT reset by writing a 1 to the CCF5 flag (PCA0CN.5) while the WDT is
enabled.
28.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
Disable the WDT by writing a 0 to the WDTE bit.
Select the desired PCA clock source (with the CPS2–CPS0 bits).
Load PCA0CPL5 with the desired WDT update offset value.
Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
mode).
Enable the WDT by setting the WDTE bit to 1.
Reset the WDT timer by writing to PCA0CPH5.
The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog
timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the
WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing
the WDTE bit.
The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by
12, PCA0L defaults to 0x00, and PCA0CPL5 defaults to 0x00. Using Equation 28.5, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 28.3 lists some example time-
out intervals for typical system clocks.
Table 28.3. Watchdog Timer Timeout Intervals1
System Clock (Hz)
24,500,000
PCA0CPL5
255
Timeout Interval (ms)
32.1
16.2
24,500,000
128
24,500,000
32
4.1
2
3,062,500
255
257
2
3,062,500
128
129.5
33.1
2
3,062,500
32
32,000
32,000
32,000
255
24576
12384
3168
128
32
Notes:
1. Assumes SYSCLK/12 as the PCA clock source, and a PCA0L value
of 0x00 at the update time.
2. Internal SYSCLK reset frequency = Internal Oscillator divided by 8.
364
Rev. 1.0
SILICON [ SILICON ]
