| HOME | SOMs | SBCs | ToloMEO Embedded Assistant |  GET A QUOTE
|
 ONLINE HELPDESK
|
| Roadmap | IoT Services | ML/AI services | Embedded Design Services |
| History | |||
|---|---|---|---|
| Issue Date | Notes | ||
| First version | |||
| 2023/07/17 | Revision of signals connections | ||
An external watchdog timer (WDT), Maxim MAX6373[1]), 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.
The default mounting option is depicted in the following figure.
WDI is connected to Zynq's PS_MIO15_500 I/O. This signal is available on Bora connectors as PS_MIO15_500 (J1.42).
MAX6373 timeout is pin-selectable. It can be configured through the WD_SET0, WD_SET1 and WD_SET2 signals. The pins are configured internally to the BORA Lite SOM, by default, as follows:
- WD_SET2 = 1
- WD_SET1 = 1
- WD_SET0 = 0
This set selects the option (the exhaustive list of configurations options is described in table 1 of reference [1]):
- tDELAY = first edge
- tWD = 10s.
In other words, WDT is started when the first transition on WDI input is detected. Once started, its timeout period is 10s. A 2.2kOhm pull-down is internally connected to the PS_MIO15_500 signal in order to avoid WDT may be inadvertently started at power-up. In general, the first transition of WDI input should be under software control (connected to PS_MIO15_500 GPIO pad) .
In any case, when the watchdog is started, the software (bootloader/operating system) must take care of toggling the watchdog trigger pin (WDI) before the timeout expiration.
Selecting different configurationsEdit
Since WD_SETx signals are routed internally, WDT configuration can be changed by ordering a Custom BORA Lite configuration: please contact our Sales department for a Custom BORA Lite order code.
It is also worth mentioning that Zynq integrates a System Watchdog Timer (SWDT) that can optionally generate 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 Sales Department.