
Table 30-2. Watchdog timeout availability (continued)
Reference clock
Prescaler
Watchdog time-out availability
÷256
256 µs–16.777 s
20 MHz (from bus or external)
Pass through
50 ns–3.277 ms
÷256
12.8 µs–838.8 ms
1. The default timeout value after reset is approximately 1 s (if LPO_CLK = 1 kHz), or 1/128 s (if LPO_CLK = 128 kHz).
NOTE
When the programmer switches clock sources during
reconfiguration, the watchdog hardware holds the counter at
zero for 2.5 periods of the previous clock source and 2.5
periods of the new clock source after the configuration time
period (128 bus clocks) ends. This delay ensures a smooth
transition before restarting the counter with the new
configuration.
30.4.2 Watchdog refresh mechanism
The watchdog resets the MCU if the watchdog counter is not refreshed. A robust refresh
mechanism makes it very unlikely that the watchdog can be refreshed by runaway code.
To refresh the watchdog counter, software must execute a refresh write sequence before
the timeout period expires. In addition, if window mode is used, software must not start
the refresh sequence until after the time value set in the WIN register. See the following
figure.
Functional description
Kinetis KE1xF Sub-Family Reference Manual, Rev. 4, 06/2019
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NXP Semiconductors
Summary of Contents for KE1xF Series
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