From Industrial Data Communications 4th Edition

We've already introduced the concept of serial communications, the placing of one bit
after another on a single media channel. It is the most prevalent form of data communications.
However, there are many differences between transmitting a text file by modem to a
bulletin board and sending data to the server over a 100-Mbps network. Both are serial,
but they differ in many ways. This chapter focuses on three EIA/TIA serial standards for
232, 422, and 485 as well as the ancillary 423 and 530 standards. Since the United States
now sits on the international standards committees, the EIA/TIA standards have their equivalency
in ISO standards, and indeed most have been changed to meet the ISO standards.
Serial interface to the PC is being accomplished by newer and much faster technologies, so
we will also focus on four PC-based standards, USB 2.0, Firewire (IEEE 1394), SATA, and
PCIe, that will impact industrial use and applications.

Definitions
Understanding how data circuit-terminating equipment (DCE) and data terminal equipment
(DTE) are defined is essential to any discussion of data communications. From the hardware
device dominant in the 1960s to today's software interfaces these terms are used
throughout data communications applications (and not always...


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© 2008 ISA

Products & Services
RS-232, RS-422, and RS-485 Interfaces
RS-232, RS-422, and RS-485 are standard interfaces approved by the Electronic Industries Association (EIA) for connecting serial devices. They are serial communication standards providing asynchronous communication capability with hardware flow control, software flow control, and parity check.
Digital Parallel and Serial Converters
Digital parallel and serial converters change input streams of parallel data into output streams of serial bits, or vice versa.
PCMCIA Serial Adapter Cards
PCMCIA serial adapter cards provide one or more serial ports to a host computer. They use a PCMCIA card bus to interface with the host, and add RS232, RS422, RS485, or other types of serial ports.
Digital Delay Generators
Digital delay generators produce pulses at precise, programmed intervals to trigger devices under test. They are also used for gating, timing, triggering, and syncing.
D-Subminiature Connectors
D-subminiature or D-sub connectors are sturdy electrical connectors with a mating face shaped like the letter D. They provide polarization because male and female connectors can fit together in only one way.

Topics of Interest

How We Got Here Thus far, we have looked at some communication models and some of the prevalent serial communications standards. In the natural progression from standalone to networked systems we now...

We’ve already introduced the concept of serial communications, the placing of one bit after another on a single media channel. It is the most prevalent form of data communications. However,...

RS-232 is the most known serial port used in transmitting the data in communication and interface. Even though a serial port is harder to program than the parallel port, this is the most effective...

Serial interfaces transmit data one bit at a time. Common standards include RS232, RS422, and RS485. The RS232 standard is approved by the Electronic Industries Association (EIA) for connecting serial...

D

D D/A or DAC Abbreviation for digital-to-analog converter. A device used to convert digital signals to analog signals. Dark Current The induced current that exists in a reversed biased photodiode in...