©
CIAS Elettronica S.r.l.
Ed. 1.2
Installation Handbook
page
46
of
55
CORAL-S
3.4.2 RS -485 Serial Line connections
The way of laying down the cable must be “multidrop” type (BUS), and the derivations for units
connection as short as possible. Using the Repeater/Regenerator and interface multipliers (BUS
REP) it is possible to make others cabling configurations like:full Star type, mixed, Star and BUS
type. Connect to the terminal 4 “LO” (“RS 485 –“ negative data line ); to the terminal 3 “LH” (“RS
485+” positive data line ) and to the terminal 2 “GND” (data ground line) of the terminal block
MS3 for the Receiver PCB and MS5 for the Transmitter PCB. To connect a PC on serial line it is
necessary to use a serial line converter RS 485/232 included in MWA TEST SW.
Cable to connect the heads (Rx and Tx)
To the maintenance P. C. with MWA TEST Software
Terminal
Block MS3
PIN
25 pin (D
Type)
Connector
of the
converter
N° N°
Symbol
Function
1 12
+13,8
Power supply (13,8 V
) per for 485/232 converter
2 9
GND
Ground data and power supply for 485/232 converter
3 10
LH 485
High Line for RS 485
4 11
LO 485
Low Line for RS 485
3.4.3 Network Configuration and Signal Repeaters
The interconnection cable concerning barrier management through a remote P.C. must be
suitable for a RS485 serial data line, i.e., it must be a
low capacity cable with 3 twisted and
shielded leads (70 pF/mt
.) for example “Belden 9842”.The limit distances of the RS 485
connection is 1200 meters. For longer distances use one or more interface Regenerators (BUS
REP), see figure 11. The way of laying down the cable must be of BUS type, and the derivations
for units connection as short as possible. It is possible to lay down the cable in different manner:
full stellar; mixed, stellar and BUS type, using Repeaters/Regenerators and interface multipliers
(BUS REP), see figure 11. The total number of units (Tx and Rx) that can be connected to the
line are 32, for an higher number of units, it is necessary the use of one or more line regenerators
RS 485, this is true also in case of cable length lower than 1200 metres. Shield connection
continuity must be guaranteed to properly protect the cited line from induced noise. To this
concern the shield will have to be GROUNDED only in one point, i.e., near the power supply unit.
The power supply voltage to the RS485 / RS 232 interface converter must be delivered by a local
power supply unit, which will have to be placed near the converter proper
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