Control Microsystems SCADAPack 32 - RS-485 Serial Communication Port; Modular Connector for RS-485; Figure 14: RS-232 DTE to RS-232 DCE; Figure 15: Front View of an RJ-45 Connector for RS-485

RS-232 COM port (DTE) DCE
2
3
4
5
6
7
8
9
1
DCD
RxD
TxD
DT
R
GND
RT
S
CT
S
+5V
DCD
RxD
TxD
DTR
GND
RTS
CTS
See devic
e
specification
s
for
p
in number
s
Figure 14: RS-232 DTE to RS-232 DCE
9.6 RS-485 Serial Communication Port
Serial port COM1 on the SCADAPack 32 controller may be configured as an RS-485 serial
communication port. A jumper must be installed on J9 to operate COM1 in RS-485 mode. Refer to
Figure 1: 5232 Controller Board Layout for the location of J9.
When configured as a RS-485 port COM1 transmits and receives differential voltages to other RS-
485 devices on a network. The RS-485 specification allows a maximum of 32 devices connected on
a single RS-485 network. The recommended specification for RS-485 is the cable length should not
exceed a maximum of 4000 feet or 1200 meters. Termination resistors are required when using long
cable lengths and high baud rates. Refer to the RS-485 Termination Resistors subsection for more
information.
The signal grounds of the RS-485 devices in the network are not connected together but instead are
referenced to their respective incoming electrical grounds. The grounds of the RS-485 devices on the
network must be within several volts of each other.
The RS-485 port operates in two or four wire mode.
9.6.1 RJ-45 Modular Connector for RS-485
The following diagram shows the pin connections for the RS-485 (RJ-45) port connector for COM1.
RJ-45 Modular Jack
Black
1. +5V
2. –Rx
3. –Tx
4. GND
5. +Rx
6. +Tx
7. Do not
connect
8. Do not
connect
2
1
8
7
6
5
4
3
Figure 15: Front View of an RJ-45 Connector for RS-485
SCADAPack 32 Controller Hardware Manual
May 24, 2006
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