Kontron PCI-COM422, Руководство пользователя

Страница: 15 / 36

PCI-COM422 User’s Guide page 15
Chapter 1: Introduction
Description
The Serial Interface Card was designed for effective transmission in RS422 (EIS422)
protocol. The card is 7.83 inches long and may be installed in PCI-bus slots of IBM PC
or compatible computers. The card features eight independent, asynchronous RS422
serial ports, type 16550 buffered UARTs.
RS422 Balanced Mode Operation
The card supports RS422 communications and uses differential balanced drivers for
long range and noise immunity. It also has the capability to add load resistors to
terminate the communications lines. RS422 communications requires that a transmitter
supply a bias voltage to ensure a known "zero" state. Also, receiver inputs at each end
of the network should be terminated to eliminate "ringing". The card supports biasing by
default and supports termination by jumpers on the card. If your application requires the
transmitter to be un-biased, please contact the factory.
COM Port Compatibility
Type 16550 UARTs are used as the Asynchronous Communication Element (ACE).
These include a 16-byte transmit/receive buffer to protect against lost data in
multitasking operating systems, while maintaining 100% compatibility with the original
IBM serial port. The system assigns the address(es).
A crystal oscillator is located on the card. This oscillator permits precise selection of
baud rates up to 115,200 or, by changing a jumper, up to 921,600 with the standard
crystal oscillator.
The driver/receiver used, the SN75176B, is capable of driving extremely long
communication lines at high baud rates. It can drive up to +60 mA on balanced lines
and receive inputs as low as 200 mV differential signal superimposed on common mode
noise of +12 V or -7 V. In case of communication conflict, the driver/receivers feature
thermal shutdown.
Communication Mode
The card supports Full-Duplex and Half-Duplex communications with a 4-wire cable
connection. Half-Duplex allows traffic to travel in both directions, but only one way at a
time.