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Using the SRDC Data Concentrator
Implementation Examples

Abstract: The SR-DC Data Concentrator can be used to provide advanced RS-232 data interleaving or multiplexing in a paired configuration or stand-alone when using a customer provided PC or workstation to decode the data. It is especially useful on non-error corrected, one-way data links and to combine multiple log outputs into a single logging stream.

In addition to its most common use in pairs as a specialized multiplexer, the SR-DC data concentrator multiplexer can be used in a single-ended application with customer supplied hardware. The customers hardware decodes the multiplexed protocol to separate individual data streams from the single composite data stream. The program that drives this hardware is usually part of the customers primary application program, but may be a stand-alone PC or embedded processor used in conjunction with other devices. However, if a stand-alone processor is required to decode the data into individual streams, it is usually more cost effective to use the SR-DC in pairs.

Example 1 illustrates the normal use of SR-DC data concentrators in pairs. This is a standard multiplexer application, except that the SR-DC has the ability of functioning through a simplex link (one-way link), and has no error-correction between the two units. Most multiplexers require a full duplex link between the units, as they pass configuration and error-correction information between themselves. This unique ability of the SR-DC to operate on a one-way link sets it apart from standard multiplexers. It can also pass data in both directions using a slow, half-duplex path such as a satellite link. Satellite links with slow round-trip times prevent most multiplexers from efficiently handshaking. This normally destroys the throughput, but the SR-DC efficiently handles this situation.

Example 1 SR-DC In a Standard Multiplexer Application

Example 2 illustrates a single-ended application of the SR-DC data concentrator. At the first location, multiple data streams are multiplexed into a single data stream (the composite) for transmission to the second location. At the second location, non-DCB hardware is used to decode the composite data stream into the individual data streams that were presented to the ports of the remote SR-DC. This is usually an application program running on a PC. Commonly used in industrial settings for data acquisition, this application program may analyze the data streams and act upon the information by sending properly formatted information back to the SR-DC. This data is presented at the appropriate output port to control a remote device. Or, the input data may simply be logged in the proper data file for future analysis.

Example 2 Single-ended SR-DC Application

In Example 3, a single SR-DC data concentrator is set up with a carriage return character as the data delimiter character. This method allows multiple data streams to be placed one after another without interleaving the "messages" from each port. An example of this usage would be multiple alarm or log messages being combined into one stream for display on a remote PC using a simple terminal emulation program.

The SR-DC protocol is relatively simple and easily decoded by a PC using customer-written software. The protocol document is available at no cost from DCB. A non-disclosure agreement is required prior to shipping the document.

Example 3 Single-ended SR-DC Application for Logging

The one-way feature is also useful in applications with a multi-drop link such as multi-point radios or a satellite up-link with multiple downlinks. This is illustrated in example 4.

Example 4 Multi-drop One-Way SR-DC Application

The SR-DC is a versatile data concentrator or multiplexer. It can be used in standard multiplexing applications, for interleaving multiple data streams into a single logging printer, or for one-way data broadcast. The unit is available with 4, 8, 16, 24, or 32 RS-232 ports. See the Data sheet here.
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