Data On Rs485 Serial Communication Module Cable - Hitachi 670 Series Installation Manual

Section 6
Connecting
2.3.1
2.3.2
The termination network below required at each end of each Bus Ph-segment.
ExV is supplied by the Node at end of the Bus Segment
The specifications of the components are:
2.3.3
The end node in each Ph-segment applies 5 V bus excitation power to the Termination network via
the Excitation pair (ExV+ and GND) used in the Type 3 Physical layer specification.
6.4.3

Data on RS485 serial communication module cable

Type:
Shield:
Length:
Table continues on next page
72
Requirements
a) The RS485 specification requires the Signal A and Signal B wires.
b) Each node also requires (5 V) Excitation of the RS485 termination network.
c) Vim - the common mode voltage between any pair of RS485 chips may not exceed 10
V.
d) A physical ground connection between all RS485 circuits will reduce noise.
Bus segment termination network
ExV+
Signal B
Signal A
DGND
ExV is supplied by the Node at end of the Bus Segment
IEC03000112 V1 EN-US
Figure 47: RS-485 bus segment termination
a) Ru + 5 V to Signal B
b) Rt Signal B to Signal A
c) Rd Signal A to GND
Bus power distribution
Twisted-pair S-STP (Screened – Screened Twisted Pair)
Individual foil for each pair with overall copper braid
Maximum 1200 m (3000 ft) from one system ground to the next system ground (includes length from
platform point to system ground on both sides)
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Ru = 390 ohm
1/4 W, 2%
Rt = 220 ohm
1/4 W, 2%
Rd = 390 ohm
1/4 W, 2%
en03000112.vsd
= 390 W, 0.25 W ±2.5%
= 220 W, 0.25 W ±2.5%
= 390 W, 0.25 W ±2.5%
1MRK514026-UUS Rev. P
SEMOD176342-280 v2
670 series
Installation manual