User Manual

SubCompact Board GENE-9455 Rev.B
Appendix A Programming the Watchdog Timer A-3
There are three steps to complete t he configuration setup: (1) Enter
the MB PnP Mode; (2) Mo dify the data of configuration re gisters; (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 operations are to
be performed during Wait for Key state. To ensure the initial state of
the key-chec k logic, it is nece ssary to p erform four write ope ra-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 a ccessi ng a selected register, the content of
Index 07h must be changed to the LDN to which the registe r
belongs, except some Global regi sters.
(3) Exit the MB PnP Mode
Set bit 1 of the configure control register (Index=02h) to 1 to exit the
MB PnP Mode.