Installation guide

Compact Board PCM- 8500
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.
Undesired 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 operations are to
be performed during Wait for Key state. To ensure the initial state of
the key-check logic, it is necessary to perform four write operations
to the Special Address port (2EH). Two different enter keys are
provided to select 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 which the register belongs, except
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
Configure Control
07H
71H R/W 00H WatchDog Timer Control Register
07H
72H R/W 00H WatchDog Timer Configuration Register
07H 73H R/W 00H WatchDog Timer Time-out Value
Register