The following table provides a description of the function of each pin of the RJ-45 connector.
Pin
Function
Description
1 5V
(Output)
This pin can be connected to the 5V power supply by
installing a jumper at J14 on the SCADAPack 350.
2
NC
Not used in RS-485 mode. Should be left open.
3
NC
Not used in RS-485 mode. Should be left open.
4
GND
This pin is connected to the system ground.
5 B
(Input/
Output)
For RS-485 operation J13 must have the jumper link in
position “RS-485”
This pin is the B signal of the RS-485 bus.
6 A
(Input/
Output)
For RS-485 operation J13 must have the jumper link in
position “RS-485”
his pin is the A signal of the RS-485 bus.
7
NC
Not used in RS-485 mode. Should be left open.
8
NC
Not used in RS-485 mode. Should be left open.
Connections to COM2 are made through a RJ-45 modular connector. COM2 supports two signals
plus Ground and 5V power. The following diagram shows the pin connections for the RS-485 (RJ-
45) port connector for COM2 operating in RS-485 mode.
RJ-45 Modular Jack
1.
+5V
2.
NC *
3.
NC *
4.
GND
5.
B
6.
A
7.
NC *
8.
NC *
* Should be left open
2
1
8
7
6
5
4
3
Figure 17: COM2 RJ-45 Connector
10.2.3
RS-485 Bias Resistors
The RS-485 receiver inputs on the controller are biased to ensure that that received data is driven to a
valid state (space) when there are no active drivers on the network. The value of these bias resistors
is 5100 ohms from Ground to the B inputs and 5100 ohms from +5V to the A inputs.
10.2.4
RS-485 Termination Resistors
Termination resistors are required in long networks operating at the highest baud rates. Networks as
long 4000 ft. operating at 9600 baud will function without termination resistors. Terminations should
only be considered if the baud rate is higher.
When termination resistors are required, they are installed on the first and last station on the RS-485
wire pair. All other stations should not have termination resistors.
SCADAPack 350 Hardware Manual
February 14, 2007
40
