JN516X Datasheet, PDF (23/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

detected and used to cause an interrupt to the processor, when the voltage either drops below the threshold or rises
above it.
The supply voltage detect is enabled by default from power-up and can extend the reset during power-up. This will
keep the CPU in reset until the voltage exceeds the SVM threshold voltage. The threshold voltage is configurable to
1.95V, 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.7V and 3.0V and is controllable by software. From power-up the threshold is
set by a setting within the flash and the default chip configuration is for the 2.0V threshold. It is expected that the
threshold is set to the minimum needed by the system..
6.5 Watchdog Timer
A watchdog timer is provided to guard against software lockups. It operates by counting cycles of the high-speed RC
system clock. A pre-scaler is provided to allow the expiry period to be set between typically 8ms and 16.4 seconds
(dependent on high-speed RC accuracy: +30%, -15%). Failure to restart the watchdog timer within the pre-configured
timer period will cause a chip reset to be performed. A status bit is set if the watchdog was triggered so that the
software can differentiate watchdog initiated resets from other resets, and can perform any required recovery once it
restarts. Optionally, the watchdog can cause an exception rather than a reset, this preserves the state of the memory
and is useful for debugging.
After power up, reset, start from deep sleep or start from sleep, the watchdog is always enabled with the largest
timeout period and will commence counting as if it had just been restarted. Under software control the watchdog can
be disabled. If it is enabled, the user must regularly restart the watchdog timer to stop it from expiring and causing a
reset. The watchdog runs continuously, even during doze, however the watchdog does not operate during sleep or
deep sleep, or when the hardware debugger has taken control of the CPU. It will recommence automatically if
enabled once the debugger un-stalls the CPU.
© NXP Laboratories UK 2013
JN-DS-JN516x v1.1 Production
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