23.0 Watchdog [T-Series Datasheet]

Overview

The Watchdog system can perform various actions if the T-Series device does not receive any communication within a specified timeout period.

A typical usage is to first use the IO Config system to set the power-up defaults for everything as desired, and then configure the watchdog to reset the device on timeout.  For example, consider a software program that enables the watchdog to reset the T-Series device with a 60 second timeout, and then the software has a loop that talks to the device once per second.  If something goes wrong with the software, or some other problem that causes communication to stop, the T-Series device will reset every 60 seconds until communication resumes.

The watchdog timeout can be set as low as 1 second, but such a low value is usually not a good idea.  For example, when a USB device resets it takes a little time for USB to re-enumerate and software to be able to talk to the device again, so you could get in a situation where the device keeps resetting so often that you can't start talking to it again.  This might require using the reset-to-factory jumper—see 11.0 SPC for details.

The timeout period is reset when a response to a command-response packet is sent to the host. Alternatively, "strict" mode can be enabled. When strict mode is enabled the timeout period is reset by writing the key value to WATCHDOG_STRICT_CLEAR. The key can be set by writing WATCHDOG_STRICT_KEY_DEFAULT. While strict is disabled writing any value to WATCHDOG_STRICT_CLEAR will clear the watchdog. Note that writing to WATCHDOG_STRICT_CLEAR will clear the watchdog when the write is processed, not when a response packet is sent.

Register Listing

Use the following registers to configure the watchdog system:

Example

The most common way to use Watchdog is to write:

WATCHDOG_ENABLE_DEFAULT=0
WATCHDOG_TIMEOUT_S_DEFAULT=60
WATCHDOG_RESET_ENABLE_DEFAULT=1
WATCHDOG_ENABLE_DEFAULT=1

If the device does not receive any communication for 60 seconds, the watchdog will cause the device to reset.  So if nothing is talking to the device, it will reset every 60 seconds.  In conjunction, you would often use the IO Config system to configure the power-up defaults as desired.