Acces PCI-ICM422/2, Руководство пользователя

Страница: 23 / 33

Page 5-1
Manual MPCI-ICM4S.F1b
Chapter 5: Programming
There are sample programs provided with the card in C, Pascal, QuickBASIC, and several
Windows languages. DOS samples are located in the DOS directory and Windows samples are
located in the WIN32 directory.
Initialization
Initializing the chip requires knowledge of the UART's register set. The first step is to set the baud
rate divisor. You do this by first setting the DLAB (Divisor Latch Access Bit) high. This bit is Bit
7 at Base A3. In C code, the call would be:
outportb(BA3,0x80);
You then load the divisor into Base A0 (low byte) and Base A1 (high byte). The
following equation defines the relationship between baud rate and divisor:
desired baud rate = (UART clock frequency) / (32 * divisor)