Emerson ROC827 instruction manual EIA-422/485 RS-422/485 Jumpers & Termination Resistors

ROC827 Instruction Manual

EIA-422/485 (RS-422/485) communication modules include LED indicators that display the status of receive and transmit activity. Refer to Tables 5-9 and 5-10.

Table 5-9. EIA-422 (RS-422) Signal Routing – Comm3, Comm4, and Comm5

Signal	RS-422	Function	Terminal
A	RX +	Lit when module (Comm3, Comm4, or Comm5) is currently receiving.	1
B	RX –	None.	2
Y	TX +	Lit when module (Comm3, Comm4, or Comm5) is currently transmitting.	3
Z	TX –	None.	4
COM	Common	Ground.	5

Table 5-10. EIA-485 (RS-485) Signal Routing – Comm3, Comm4, and Comm5

Signal	RS-485	Function	Terminal
A	RX / TX +	Lit when module (Comm3, Comm4, or Comm5) is currently receiving.	1
B	RX / TX –	Lit when module (Comm3, Comm4, or Comm5) is currently transmitting.	2
Y	No Connect	None.	3
Z	No Connect	None.	4
COM	Common	Ground.	5

Note: The EIA-422/485 (RS-422/485) modules are isolated on the field side. Be aware that you can induce ground loops by tying commons together.

EIA-422/485 (RS-422/485) communications provides EIA-422/485 (RS- 422/485) signals on the Comm3, Comm4, or Comm5 port, depending on where the module is installed. Wiring should be twisted-pair cable, one pair for transmitting, and one pair for receiving. The EIA-422 (RS-422) module uses four wires and the EIA-485 (RS-485) uses two wires for connectivity.

5.8.1 EIA-422/485 (RS-422/485) Jumpers & Termination Resistors

Four jumpers—J3, J4, J5, and J6—are located on the EIA-422/485 (RS- 422/485) communications module. These jumpers determine the mode in which the module runs (RS-422 or RS-485) and if the module is terminated.

Terminations are required on the two EIA-422/485 (RS-422/485) communication modules located at the extremities of the circuit. That is to say, the two outside modules require terminations in order to complete the communications circuit.

Issued Mar-06 Communications 5-11