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ROC827 Instruction Manual

Issued Mar-06 Communications 5-11

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.

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Emerson ROC827 Manuel d'utilisateur Page 103