4
Operation Theory
In
1.Direct Program Control: the digital inputs and outputs can be read/written and controlled by its corresponding I/O port address directly.
2.Internal Timer Pacer Mode: the digital input and output operations are paced by an internal timer pacer and are transferred by bus mastering DMA.
3.External Clock Mode: the digital input operation is clocked by external I_REQ strobe and transferred by bus mastering DMA.
4.Handshaking: through REQ and ACK signals, the digital I/O can have simple handshaking data transfers.
4.1 Direct Program Control
Digital I/O operations can be controlled by I/O port BASE+10 for digital input and BASE+14 for digital output.
The I/O port address BASE is assigned by system BIOS, please refer to Section 5 for a more detailed description.
The digital OUT operation is:
outport (BASE+14, 0xAAAAAAAA) // (A : 0 to F)
The digital IN operation is:
value = inport (BASE+10) // The input status is save in the // value variable
Operation Theory • 29
