Specifications

Chapter 9 l l RS-232/RS-422/RS-482 Programming

outportb(BASE + 4, 3);

Or use the following function in API-232 library:

sio_RTS(port, 1);

A statement as following will clear the RTS signal and turn off the transmitter :

outportb(BASE + 4, 0);

Or use the following function in API-232 library:

sio_RTS(port, 0);

Besides, the following function in API-232 library is provided especially for

RS-485 programming:

sio_putb_x();

Please refer to API-232 User's Manual for more details.

2. REG

The transmitter(or receiver) is controlled by the control register BASE + 7 bit 1

(or bit 0), where BASE is the base I/O address of the port. When the

corresponding bit is set to "1", the transmitter/receiver is enabled. Setting the bit

to "0" will turn the transmitter/receiver off to high impedance status and the

16x50 UART chip will not transmit/receive any signal. In Turbo C language, a

statement as following will turn on the transmitter :

outportb(BASE + 7, 1);

A statement as following will turn on the receiver:

outportb(BASE + 7, 2);

A statement as following will turn off both the transmitter and receiver:

outportb(BASE + 7, 0);