Installation 1-9
September 2004
Wiring the Serial Port The Model AT868 flow transmitter is equipped with a built-in serial
communications port. The standard port is an RS232 interface, but an
optional RS485 interface is available upon request. Proceed to the
appropriate sub-section for wiring instructions. For more information
on serial communications refer to the EIA-RS Serial Communications
Manual (916-054).
Wiring an RS232 Interface Use the serial port to connect the Model AT868 flow transmitter to a
printer, an ANSI terminal or a personal computer. The RS232
interface is wired as Data Terminal Equipment (DTE), and the signals
available at the COMMUNICATION terminal block are shown in
Table 1-1 below.
1. Follow the instructions on page 1-4 to prepare the unit before you
connect power.
2. Use the information in Table 1-1 below to construct a suitable
cable for connecting the Model AT868 to the external device. If
desired, an appropriate cable may be purchased from the factory.
Note: Signal names that imply direction (e.g., transmit and receive)
are named from the point of view of the DTE device (the GE
Infrastructure Sensing meter is usually considered the DTE
device). When the RS232 standard is strictly followed, these
signals are labeled with the same name and pin # on the DCE
device side as well. Unfortunately, the convention is not
followed because the DTE and DCE side get confused.
Therefore, connections that imply direction are changed to
reflect their direction on the DCE side.
Table 1-1: RS232 Connection to DCE or DTE Device
COMMUNICATION
TB
Colors for GE
Infrastructure
Sensing Cable
(flying leads)*
Signal
Description
DCE
DB25
Pin #
DCE
DB9
Pin #
DTE
DB25
Pin #
DTE
DB9
Pin #
5 White
DTR (Data
Terminal Ready)
204204
4 Yellow
CTS
(Clear to Send)
4758
3 Green COM (Ground)7575
2 Red RX (Receive)2332
1 Black TX (Transmit)3223
*For standard GE Infrastructure Sensing cables 704-659, -660, -661 and -662.
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