RTS XCP-48-RJ45 Especificações descarregar pdf (Página 33)

Chapter 8 EIA-485 Asynchronous Interface 33

General EIA-485 Cable Information

This section applies to Digi products equipped with EIA-485 asynchronous

interfaces.

Physical Cable Characteristics

EIA-485 interface cables should be shielded twisted-pair cables with a

maximum of 4000 feet in length. Each signal requires two leads (one

twisted pair of wires) to complete a balanced voltage digital circuit. The

shield should be connected to the Chassis Ground of the devices at both

ends of the interface cable.

Interface Signaling

The EIA-485 interface provides four signals: Transmitted Data (TxD),

Received Data (RxD), Request To Send (RTS) and Clear To Send (CTS).

The functions of these signals are identical to their EIA-232 counterparts.

Grounding Requirements

EIA-485 interface cables must provide a ground path between the devices

to be connected. This ensures the integrity of data transfers and control

signals. This should be connected to the Chassis Ground of each device.

Digi recommends using the cable shield for this purpose.

Termination Information

A DIP switch controls the termination of many Digi devices. Most Digi

devices use the #4 switch to control termination. When the switch is down,

termination is off and there is no termination. To set termination on the

device, move the #4 switch to the up position. Termination is recommended

in a multi-drop line for the last networked device. Termination also biases

the line.

Check your Digi device for its ohm rating, but 100 ohms is the nominal

setting in Digi products.

Chapter 6

EIA-485 Asynchronous Interface

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RTS XCP-48-RJ45 Especificações Página 33