Modular Connector For Rs-485; Rs-485 Bias Resistors - Control Microsystems SCADAPack 32P Hardware Manual

The RS-485 port operates in two or four wire mode.
4.4.1 RJ-45 Modular Connector for RS-485
The following diagram shows the pin connections for the RS-485 (RJ-45) port connector for COM1.
+5V is only available on Pin 1 when a jumper is installed on J4. Refer to section 3.1-Field Wiring
Connections for the location of J4.
Serial port COM1 may be configured as RS-232 or RS-485. A jumper must be installed on J9 to
operate COM1 in RS-485 mode. Refer to section 3.1- Field Wiring Connections for the location of
J9.
The differential receive and transmit signals are labeled +/–Rx and +/–Tx respectively. Some RS-485
devices refer to the – side of the signal as A and the + side of the signal as B.
The following table provides a description of the function of each pin of the RJ-45 connector. In this
table a MARK level is a voltage of +3V or greater and a SPACE level is a voltage of –3V or less.
Pin Function
1 5V
(Output)
2 -Rx
(Input)
3 -Tx
(Output)
4 GND
5 +Rx
(Input)
6 +Tx
(Output)
7 N/C
8 N/C
4.4.2

RS-485 Bias Resistors

The RS-485 receiver inputs on the SCADAPack 32P 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 4700 ohms from Ground to the –Rx input and 4700 ohms from +5V to the +Rx
input.
SCADAPack 32P Controller Hardware Manual
May 26, 2006
RJ -45 Modular J ack
Black
1 2 3 4 5 6 7
Description
This pin can be connected to the 5V power supply by installing a
jumper at J4 on the SCADAPack 32P.
The DCD led is on for a MARK level.
This pin is normally at a MARK level.
This pin is at a SPACE level when DTR is de-asserted.
This pin is connected to the system ground.
The level is SPACE on standby and MARK for received data.
The LED is lit for a MARK level.
The level is SPACE on standby and MARK for transmitted data.
The LED is lit for a MARK level.
Do not connect this pin for RS-485 operation.
Do not connect this pin for RS-485 operation.
1. + 5V
2. –Rx
8
3. –Tx
4. GND
5. + Rx
6. + Tx
7. Do not
connect
8. Do not
connect
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