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Promi-SD 205-OA User Manual – 3. Connections
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 communicati on, 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 #
1
2
3
4
5
6
7
8
9
Signal
Direction
N/A
-
RxD
Input
TxD
Output
N/A
-
N/A
-
Vcc
Input
N/A
-
N/A
-
GND
-
Copyright © 2006 Sena Technologies, Inc. All rights reserved.
Description
Received Data
Transmitted Data
Ring Indicator
Signal Ground
23
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