AAEON EPIC-9457 Rev.B - Manual (Page 44)

E P I C B o a r d E P I C - 9 4 5 7 R e v . B
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.
(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.