Specifications

AMD Geodeā„¢ GeodeROM Functional Specification 85
Serial Port BIOS Support
32087C
8.1.2 Function 01h - Write Character to Port
Description:
Sends a character of data to the serial port.
Passed:
Returns:
8.1.3 Function 02h - Read Character from Port
Description:
Reads a byte of data from the serial port. Function does not return until data is available or a timeout has occurred.
The caller may invoke Function 03h (Get Port Status) to check whether data is available to be read.
Passed:
Returns:
Parameter Description
AH 01h
AL ASCII code for the character
DX Port number:
See "Function 00h - Initialize Port" on page 83
Parameter Description
AH 00h if no error occurred
8xh indicates an error occurred
x represents:
6 = Transfer shift register empty
5 = Transfer holding register empty
4 = Break occurred
3 = Framing error occurred
2 = Parity error occurred
1 = Overrun error occurred
0 = Data ready
Parameter Description
AX 02h
DX Port number:
See "Function 00h - Initialize Port" on page 83
Parameter Description
AL ASCII code for the character
AH 00h if no error occurred
8xh indicates an error occurred
x represents:
6 = Transfer shift register empty
5 = Transfer holding register empty
4 = Break occurred
3 = Framing error occurred
2 = Parity error occurred
1 = Overrun error occurred
0 = Data ready