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Chapter 3 EIA-232 Asynchronous Interface 9

General EIA-232 Cable Information

Use this information to determine the proper EIA-232 cable requirements

for your application.

Physical Cable Characteristics

EIA-232 serial interface cables should be shielded, low capacitance cables,

designed specifically for serial data transmission.

Grounding Requirements

EIA-232 interface cables should have the shield grounded at both ends of

the cable. Digi recommends Chassis Ground, available on the shell of

Digi's DB-25 connectors, and pin 4 of a 10 pin RJ-45 connector.

Environmental Requirements

While good shielding provides reasonable protection against "noise"

(electromagnetic interference, or EMI), cables should still be routed away

from noise sources wherever possible. Avoid laying cables in close

proximity to transformers, generators, motors, fluorescent lights, etc.

Data Rate Information

The maximum data rate that can be used for EIA-232 connections is

primarily determined by the quality and length of the interconnecting cable.

The quality of the cable (for transmission purposes) is generally

determined by the capacitance per foot rating of the cable.

The following table gives the recommended maximum cable length for a

given data rate. Longer cables may be implemented at your discretion.

Note that not all Digi products support all of the data rates listed below.

Data Rate vs. Cable Length

Notes:

• The maximum length is the amount of cable that is connected to a

Digi supplied interconnect device, such as Quad or Octa cables and

boxes.

• The maximum length is based on a cable rated at the following:

12.3 pF/foot, conductor to conductor

22.4 pF/foot conductor to shield

Chapter 1

EIA-232 Asynchronous Interface

Data Rate (bps) Maximum Cable Length

57,600 or less 100 feet

115,200 80 feet

230,400 40 feet

460,800 20 feet

921,600 10 feet

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 151 152

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RTS XCP-48-RJ45 Dokumentacja Strona 9