Chapter6 UsingYour Serial Hardware
©NationalInstruments Corporation 6-3 SerialHardware and Software for Windows
Two-WireMode: TXRDY Auto Control
Inthis mode, the serial hardware transparently enables the transmitter and
receiverin a two-wire system. Use this mode to remove the burden of flow
control from your application. By connecting the transmitter to the
TXRDY (Transmit Ready) line, the hardware enables the transmitter for
each byte to be transmitted. Also, the hardware disables the receiver
wheneverthe transmitter is enabled, so you do not receive the packets sent
from your transmitter.
Note When you are communicating with a two-wire device, National Instruments
recommends that youuse the two-wire TXRDY auto control mode. Because this mode
handlest he transmitter/receiverenabling for a two-wire connection in your hardware,
itreduces the software overhead required to perform this operation in your application
program.
Formore information about serial communication i n two- or four-wire modes, refer to the
Serial Communication Issues sectioninAppendixB,Serial Port Information.
Setting the TransceiverControl Mode
Windows 2000
To sett he transceiver control mode, use the Windows 2000 Device
Manager.For i nstructions on how to use the Device Manager, refer to the
chapterwith installation instructions for your hardware platform.The mode
you selectin the Device Manager is automatically configured when you
open a port on a serial interface.
Windows Me/9x
To sett he transceiver control mode, use the Windows Me/9xDevice
Manager.For i nstructions on how to use the Device Manager, refer to
chapterwith installation instructions for your hardware platform . The mode
you selectin the Device Manager is automatically configured when you
open a port on a serial interface.
Youcan also set the hardware transceivercontrol mode from within a DOS
application.For each port you want to control, write the control byte for the
mode you wantto select to the scratch register of the UART. Table6-2
showsthe control bytes for each mode.