21
Morley-IAS
996-203-000-2, Rev. 02
3.4.10.1
Daisy Chain Style Installation
-
Form the peripheral RS485 link by taking
wires from the A and B terminals to the A
and B terminals of the next device on the
link.
-
Continue wiring to all the units to be
connected to the link – connecting A to A
and B to B.
-
Install EOL (150Ohms, 0.5W) resistors in
the spare terminals in both the first and last
units on the link.
-
The maximum allowed length of the link is
1.2km (4000’).
-
Shielded cable should be used for all digital
input circuits wired to switches external to
the panel.
-
Refer to
Appendix 1 Specifications
for a
list of recommended cables.
-
The above diagram and instructions are correct
for ZXr-A and ZXr-P Repeaters. (Do not re-
legend the ABAB terminals in these repeaters
with the label supplied). Also the EOL resistors
can be configured through correct jumper
settings on these repeaters – rather than using
the physical EOL resistor arrangement shown
above.
Figure 21 - Typical RS485 - ‘Daisy Chain’ Wiring
3.4.10.2
Cable Screen - Earth Connections
-
During installation of the peripheral link, the consequences of connecting remote grounds together
must be considered.
-
When wiring between RS485 circuits and/or peripherals if a drain earth wire is available it should not
be bonded to the chassis at both ends of the link.
-
The drain earth wire should only be bonded to one of the panel chasses. The other end should not be
bonded directly to the chassis but should be connected through a non-polarised 2.2
μ
Fcapacitor.
This is shown below.
Figure 22 - RS485 Screen - Earth Arrangement
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