55xGenComm1_29
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Data Communications Overview
Data Communications between two electronic devices has increased in use over recent years.
This document is intended to clarify the main points of serial data communications over two of the
most widely used hardware interfaces, RS232 and RS485.
Data communication covers many applications, from the simple monitoring of a piece of equipment
to the control of a complex plant operation. (This is often called S.C.A.D.A., which stands for
Supervisory Control And Data Acquisition).
As different manufacturers often supply the control and monitoring equipment, industry standards
were defined to specify the interface between the equipment.
DSE P810 description
Direct RS232 cable connection between the equipment is the simplest and most often used
communication interface. Care should be taken however to provide proper electrical isolation
between the equipment. The Deep Sea Electronics P810 interface is used to provide this isolation
between the 55x and 52xx range of control modules and the Personal Computer connected to the
module. Using the P810 interface has another advantage in that the operating range of the
communication link is increased to over 100m! (Maximum RS232 cable length is 15m).
RS232 description
Defined officially as the “interface between data terminal equipment and data communications
equipment using serial binary data exchange”, RS232 specifies only the hardware interface
between the equipment, and not the protocol (electronic language) that the equipment
communicates in. Protocols are discussed further below.
Data terminal equipment is typically a PC monitoring the system, while Data communications
equipment is typically a modem or other communications device. A modem (stands for Modulator /
Demodulator) is used to convert electrical signals from the equipment into audible signals suitable
for transmitting over the public switched telephone network (PSTN).
NOTE:- .
For more detailed RS232 connection details of the DSE controllers, including recommended
modem type, please consult the Link500Plus manual (55x modules) or 52xx configuration software manual
(52xx series modules).
