User Manual

Compact Board PCM-5895

Appendix A Programming the Watchdog Timer A - 3

There are three steps to complete the configuration setup: (1)

Enter the MB PnP Mode; (2) Modify the data of configuration

registers; (3) Exit the MB PnP Mode. Undesi red result may

occur if the MB PnP Mode is not exited normally.

(1) Enter the MB PnP Mode

To enter the MB PnP Mode, four special I/O write operation s

are to be performed duri ng Wait for Key state. To ensure the

initial state of the key-check logic, it is necessary to perform

four write opera-tions to the Speci al Addr ess port (2EH). Two

different enter keys are provided to sele ct configuration ports

(2Eh/2Fh) of the next step.

Address Port Data Port

87h, 01h, 55h, 55h: 2Eh 2Fh

(2) Modify the Data of the Registers

All configuration registers can be accessed after entering the

MB PnP Mode. Before accessing a selected register, the

content of Index 07h must be changed to the LDN to whi ch

the register belongs, exce pt some Global registers.

(3) Exit the MB PnP Mode

Set bit 1 of the configure control register (Index=02h) to 1 to

exit the MB PnP Mode.

WatchDog Timer Configuration Registers

LDN Index R/W Reset Configuration Register or Action

All 02H W N/A Configuration Control

07H 71H R/W 00H WatchDog Timer Control Regi ster

07H 72H R/W 00H WatchDog Timer Configuration Register

07H 73H R/W 00H WatchDog Timer Time-out Value (LSB)

07H 74H R/W 00H WatchDog Timer Time-out Value (MSB)