Installing The Serial Communication Cable For Rs485 Spa/Iec - Hitachi 670 Series Installation Manual

1MRK514026-UUS Rev. P
Drain wire
IEC07000139 V1 EN-US
Figure 46:
The EIA standard RS-485 specifies the RS485 network. An informative excerpt is given in
section "Installing the serial communication cable for RS485
6.4.2

Installing the serial communication cable for RS485 SPA/IEC

Informative excerpt from EIA Standard RS-485 - Electrical Characteristics of Generators and Receivers
for Balanced Digital Multipoint Systems
RS-485 Wire - Media dependent Physical layer
1
EIA Standard RS-485 - Electrical Characteristics of Generators and Receivers for Balanced Digital
Multipoint Systems
2
RS-485 differential bipolar signaling
2.1
Two differential signal levels are defined:
2.2
The RS485 circuit shall be isolated from ground by:
Three isolation options exist:
2.3
Table continues on next page
670 series
Installation manual
Pair separator
Jacket
Cross section of communication cable
Normative references
Transmission method
Differential signal levels
A+ =line A positive with respect to line B
A- =line A negative with respect to line B
Galvanic isolation
Riso ≥ 10 MW
Ciso ≤ 10 pF
a) The entire node electronics can be galvanically isolated
b) The bus interface circuit can be isolated form the rest of node electronics by
optoisolators, transformer coupling or otherwise.
c) The RS485 chip can include built-in isolation
Bus excitation and signal conveyance
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Pair Shield
Conductor
Overall shield
Separator
en07000139.vsd
SPA/IEC".
Section 6
Connecting
SEMOD176342-192 v3
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