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Compact Board PCM-9452
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 opera-tions 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 Configuration 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 (LSB)
Register
07H 74H R/W 00H WatchDog Timer Time-out Value (MSB)
Register