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标题: [NUC980] Enabling Watchdog Timer on NUC980 [打印本页]

作者: admin 时间: 前天 13:06
标题: [NUC980] Enabling Watchdog Timer on NUC980

The NUC980 series supports a hardware watchdog timer (WDT), which can be used to improve system robustness by resetting the system in the event of a software fault. However, the method of enabling the WDT differs depending on the chip package.

Hardware Pin Limitation (PG3)

LQFP128 & LQFP216: Has a PG3 pin which can be used to configure whether the watchdog is enabled during boot via hardware.
LQFP64: Does not have PG3 — therefore, watchdog must be enabled via software (U-Boot).

Enabling WDT in U-Boot (for LQFP64 or software control)1. Configure U-Boot to Enable NUC980 Watchdog Driver

$ make uboot-menuconfig

Navigate to:

Device Drivers --->

NUC980 Watchdog

Save and exit.

2. Rebuild U-Boot$ make uboot-rebuild
$ make

After this, U-Boot will include the NUC980 watchdog support.

Controlling WDT Activation via env.txt

In your U-Boot environment file (env.txt), add one of the following:

To disable WDT at boot:

watchdog=off # or watchdog=0

To enable WDT at boot:

watchdog=on # or watchdog=1 # or any non-zero, non-off string

If watchdog is undefined or set to any value other than off or 0, the watchdog timer will be enabled.

Default Timeout Behavior

By default, the watchdog configuration in U-Boot uses the following:

Clock source: PCLK2 / 4096
Timeout count: 1,000,000 ticks

Given:

PCLK2 = 75 MHz
WDT clock = 75,000,000 / 4096 ≈ 18,310.5 Hz
Timeout = 1,000,000 / 18,310.5 ≈ 54.6 seconds

You may modify this behavior in the U-Boot source if needed:

buildroot/output/build/uboot-custom/drivers/watchdog/nuc980_wdt.c

Reference:
https://github.com/OpenNuvoton/NUC970_U-Boot_v2016.11/blob/master/drivers/watchdog/nuc980_wdt.c

Linux Kernel Consideration

If WDT is enabled by U-Boot, the Linux kernel must either:

Periodically reset the watchdog timer during boot and runtime, or
Disable the watchdog timer once the kernel is up and running.

Since the WDT was software-activated, it can also be cleanly disabled by the Linux kernel.

Documentation Reference

Watchdog Register Map: Refer to the Watchdog Timer chapter in the [NUC980 Technical Reference Manual (TRM)].
WDT Control in U-Boot: Refer to U-Boot driver source linked above.

If you need help with modifying the timeout behavior or integrating WDT into your Linux application, please let us know.

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