Sena 205 User Manual download pdf (Page 25)

Promi-SD 205-OA User Manual – 3. Connections 23

RS232C Interface

 RS232C

In the early 1960s, a standards committee, today known as the Electronic Industries Association, developed a common

interface standard for data communications equipment. At that time, data communications was thought to mean

digital data exchange between a centrally located mainframe computer and a remote computer terminal, or possibly

between two terminals without a computer involved. These devices were linked by telephone voice lines, and

consequently required a modem at each end for signal translation. While simple in concept, the many opportunities for

data error that occur when transmitting data through an analog channel require a relatively complex design. It was

thought that a standard was needed first to ensure reliable communication, and second to enable the

interconnection of equipment produced by different manufacturers, thereby fostering the benefits of mass production

and competition. From these ideas, the RS232 standard was born. It specified signal voltages, signal timing, signal

function, a protocol for information exchange, and mechanical connectors. Refer the following site for details;

http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

 DTE/DCE

If the full EIA232 standard is implemented as defined, the equipment at the far end of the connection is named the DTE

device (Data Terminal Equipment, usually a computer or terminal), has a male DB9 connector. Equipment at the near

end of the connection (the telephone line interface) is named the DCE device (Data Circuit -terminating Equipment,

usually a modem), has a female DB9 connector. The cable linking DTE and DCE devices is a parallel straight-through

cable with no cross -overs or self-connects in the connector hoods. If all devices exactly followed this standard, all

cables would be identical, and there would be no chance that an incorrectly wired cable could be used.

 DB9 Male

Promi-SD is a DCE device compatible with RS232 standard, having DB9 male interface.

Pin Assignment

Pin # Signal Direction Description

1 N/A -

2 RxD Input

Received Data

3 TxD Output

Transmitted Data

4 N/A -

5 N/A -

6 Vcc Input

Ring Indicator

7 N/A -

8 N/A -

9 GND -

Signal Ground

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Sena 205 User Manual Page 25