IBM PCM-6890B, All-in-One FC/Socket 370 Celeron manual Watchdog timer, Configuration register

Programming the watchdog timer

Watchdog timer

The watchdog timer uses a 8-bit counter. The time range is from 32 seconds to 254.5 min with a resolution of 1 min. When timer times out, a system reset will happen.

Configuration register

The watchdog timer of PCM-6890B is located on the chipset – Winbond W83977. If you want to use it, you have to know how to read/write the configuration register of W83977. The basic proce- dure is as follows.

1.Enter configuration mode.

2.Select Logical Device.

3.Select register number.

4.Write/read data to/from register.

5.Exit configuration mode.

To Enter/Exit the configuration mode is to write a specific value to configuration port — 3F1h.

Enter configuration mode: write value 87h to configuration port twice.

Exit configuration mode: write value aah to configuration port.

102 PCM-6890B User Manual