IBM LPCI-COM-4SM, LPCI-COM-8SM, LPCI-COM232-4, LPCI-COM232-8 Chapter 1: Introduction

Chapter 1: Introduction

This serial interface card was designed for effective multipoint transmission in any one of three modes on

each channel. These modes are RS232, RS422 and RS485 (EIA485) protocol.

The RS485 mode may be run in three manners. It may be run as a standard RTS controlled channel, an

“Auto RTS (referred to by some as Auto RS485)” mode or as a “4 wire RS485 mode channel.

The card is 6.60 inches long and may be installed in 3.3 or 5-volt PCI-bus slots of IBM PC or compatible

computers. The card features eight independent, asynchronous serial ports, type 16788 buffered UARTs.

This series of cards are available in 4-port and RS-232 only versions.

The card supports RS422 communications and uses differential balanced drivers for long range and

noise immunity. The card 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.

The card supports RS485 communications and uses differential balanced drivers for long range and

noise immunity. RS485 operation involves switchable transceivers and the ability to support multiple

devices on a single "party line". The RS485 specification defines a maximum of 32 devices on a single

line. The number of devices served on a single line can be expanded by use of "repeaters".

The card also has the capability to add load resistors to terminate the communications lines. RS485

communications requires that one transmitter supply a bias voltage to ensure a known "zero" state when

all transmitters are off. 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.

Eight Type 16550 compatible UARTs incorporated within a single octal UART are used as Asynchronous

Communication Elements (ACE). These include 64-byte transmit & receive buffers to protect against lost

data in multitasking operating systems, while maintaining 100 percent 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 rate up to

115,200 or, by changing a jumper, up to 921,600 with the standard crystal oscillator.

The driver/receiver used, the SP841 in non-RS232 modes, 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.

The driver/receiver used in RS232 mode is the SP211.

Manual LPCI-COM-8SM