National Instruments 3.22E+04

Chapter 1 Introduction

Additionally, the PCI serial boards are available in a two-port version

(PCI-232/2 and PCI-485/2), a four-port version (PCI-232/4 and

PCI-485/4), an eight-port version (PCI-232/8 and PCI-485/8), and a

sixteen-port version (PCI-232/16). The two-port versions use DB-9

connectors. The four-port versions use 10-position modular jacks to

provide all four connections on a single back panel. Optional cable

accessories convert the 10-position modular jacks to either DB-9 or DB-25

connectors with standard pinouts. The eight-port versions use adapter

cables to convert the 68-pin connector on the board to eight DB-9

connectors. The sixteen-port version uses a breakout box to convert the

100-pin connector on the board to sixteen DB-9 connectors. Throughout

this manual, PCI serial boards refers to all versions of the PCI serial

boards.

The isolated PCI-232 and PCI-485 boards are designed for applications in

harsh environments. Isolated ports provide reliable communication in

situations involving ground loops from different ground levels or high

common mode voltage induced on the lines in noisy environments.

Non-isolated ports may not provide reliable communication in those

situations. The isolation between each communication port and the host PC

ensures the safe operation of the PC and the devices connected to other

ports on the same board, in case of accidental high voltages on

communication lines.

The PCI-485 boards support four hardware transceiver control modes

forreliable communication with two- and four-wire devices. For more

information about transceiver control modes, refer to Chapter4, Using

Your Serial Hardware.

All serial hardware uses standard 16550-compatible UARTs (Universal

Asynchronous Receiver/Transmitters) for complete compatibility

with standard PC COM ports. The serial hardware contains FIFOs

(First-In-First-Out) buffers to reduce susceptibility to interrupt latency

for faster transmission rates. Full Plug and Play compatibility allows

switchless configuration and installation. For more information about

the serial hardware specifications and operating conditions, refer to

Appendix D, Specifications.