Changes

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An external watchdog timer (WDT), Maxim MAX6373<ref name="MAX6373">https://www.maximintegrated.com/en/products/power/supervisors-voltage-monitors-sequencers/MAX6373.html</ref>), is connected to the PORSTn signal. During normal operation, the microprocessor should repeatedly toggle the watchdog input WDI before the selected watchdog timeout period elapses to demonstrate that the system is processing code properly. If the μP does not provide a valid watchdog input transition before the timeout period expires, the supervisor asserts a watchdog (WDO) output to signal that the system is not executing the desired instructions within the expected time frame. The watchdog output pulse is used to reset the μP.

Default mounting option is depicted in the following figure.

When the watchdog is started, the software (bootloader/operating system) must take care of toggling the watchdog trigger pin (WDI) before the timeout expiration.

Since WD_SETx signals are routed externally, WDT configuration can be changed by optional circuitry implemented on the carrier board. Different solutions can be implemented on the carrier board, depending on system requirements. The easiest circuit consists of additional stronger pull-up/down resistors connected to WD_SETx pins in order to overrule default configuration. As MAX6373 allows to change the configuration during operation, more complex solutions can be implemented as well.

It is also worth mentioning that Zynq integrates a System Watchdog Timer (SWDT) that can optionally generates a reset pulse on PS_MIO15_500 pad if this is configured as SWDT reset. In case such a configuration is of interest, on request MAX6373 may not be populated. For more details about this option, please contact [mailto:sales@dave.eu Sales Department].