Chapter 10
Serial Communication and Commands
10.1
Introduction
The Model 1094B has two RS-232/485 ports, called COM1 and COM2. COM1 combines the
two functions of RS-232 and RS-485 at one DB9M connector (J5), and COM2 combines the two
functions of RS-232 and RS-485 in a separate DB9M connector (J7). The RS-232 ports do not use
flow control, and the RS-485 ports function in transmit only mode.
Use the two serial ports interchangeably for separate functions. You may wish to interrogate the
clock on one port for basic information (i.e to configure something) and at the same time be able
to have the second serial port broadcasting a specific time code to a meter. While most recent
substation equipment has standardized on the IRIG-B time code, some devices are designed to
receive ASCII data through the serial port. Another common serial-port function is to connect a
digital wall display to indicate the time.
10.2
Communication Port Information
Table 10.1 lists functions and associated pins for both the RS-232 and RS-485 ports.
Pin No.
Function
Pin No.
Function
1
Not Connected
6
RS-232 Input
2
RS-232, Rx Data
7
Not Connected
3
RS-232, Tx Data
8
RS-422/485, Tx-A
4
RS-232 Output/Prog Pulse
9
RS-422/485, Tx-B
5
Ground
–
–
Table 10.1: COM1 and COM2 Pin Definitions