Specifications

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.
Chapter 1
EIA-232 asynchronous interface