GM82C803CN Datasheet, PDF (17/84 Pages) List of Unclassifed Manufacturers – 2.88 MB FDC/ Dual UARTs with FIFO/PIO(EPP/ ECP)/ IDE Interface/ S-IR/ PnP

GM82C803CN
3.1.19 Software Configuration procedure
Configuration is accomplished in three basic steps :
a) Enter configuration mode
b) Configure the GM82C803CN
c) Escape from configuration mode
Any deviation from this sequence causes the configuration state machine to
return to its initial idle state. The configuration procedure is intentionally
complicated to prevent an errant program from making accidental changes
to the chip configuration.
Enter Configuration Mode
Write 33h to port 398h twice consecutively.
The following is an example in 8086 assembly language:
MOV DX,398h : Port Address
MOV AL,33h : Data
OUT DX, AL
OUT DX, AL : In configuration mode
Configure the Chip
The 25 configuration registers can be written to or read from.
To read or write data from/to the registers:
1. Write index to port 398h
2. Write data to port 399h/Read data from port 399h.
(where ata?is the value to be written to/to be read
from the register which the index points to.)
Before you enable any function of the chip, you should complete
the function setting. ( Base address, IRQ, DRQ, and etc. )
Escape from Configuration Mode
Write 55h to port 398h once.
The following is an example
MOV DX, 398h : Port Address
MOV AL, 55h
: Data
OUT DX, AL
: Exit from configuration mode