LCD-160 P/N 51850:A 09/26/2003
19
The RDP Bus
Wiring
Shielding the RDP Bus
All enclosures, including the FACP backbox, must be connected to earth ground! Never use the shield for
grounding purposes.
If shielded, terminate the RDP shield at one end only.
• When the RDP shield is in conduit: Connect it to a system reference (system common). The
shield can enter the cabinet, but it must be insulated from the cabinet (no electrical contact).
Between RDP devices, wire-nut multiple shields together (These shields can be inside of the
respective enclosure, but can not contact the enclosure).
• When the RDP shield is not in conduit: Terminate the shield at the outside of the FACP
backbox (ground). Do not allow the shield to enter or even touch a cabinet that houses any
remote RDP device. Between RDP devices, wire-nut multiple shields together outside of the
respective enclosures (see Figure 7).
.
Connecting the RDP Bus
Figure 8 provides RDP circuit diagrams for the
LCD-160.
See “RDP Bus Wiring Specifications” on page 18
for circuit requirements.
End-of-Line Resistor for RDP Devices
If the LCD-160 is the last device on the RDP bus,
the end-of-line resistor on SW17 must be enabled.
SW17 is located on the bottom edge of the
LCD-160 board. Switch 2 on the dip switch SW17
sets the end-of-line resistor for the RDP bus. To
enable, use a small screwdriver to slide the switch
towards the display screen. To disable, slide the
switch away from the display screen. See Figure 9.
Remember to disable the end-of-line resistor for all
preceding devices on the RDP bus. Turn off all
power when connecting the LCD-160 to avoid
damaging the equipment.
Figure 7 Terminating the Shield (Not in Conduit)
w
ireco
nd.
pcx
Enclosure
LCD-160
RDP_
LCD160
.c
dr
+ RDP
+ RDP
- RDP
- RDP
REF
REF
EARTH
See Figure 9 to set on-board ELR for the LCD-160.
Note:
Reference connections are only necessary
when LCD-160s are powered by multiple power
supplies.
Figure 8 Connecting the RDP Bus
+ RDP
+ RDP
- RDP
- RDP
REF
REF
EARTH
+ RDP
+ RDP
- RDP
- RDP
REF
REF
EARTH
NOTE:
Switches 3 and 4
MUST
remain disabled.