Honeywell NETAXS NX4L1, Руководство по установке, Страница: 79 / 86

NetAXS™ NX4L1 Access Control Unit Installation Guide , Document 7-901099V3
79
B
Recommended Wiring for
NetAXS-4/NetAXS-123 Loops
1.0 Overview
This document provides the recommended RS-485 wiring for NetAXS-4 and mixed
loop configurations.
The downstream controller boards communicate to the gateway controller board
through an RS-485 interface. The interface allows for multidrop communication of up
to 4,000 feet (1,200 m) total per port. Use two twisted pair (minimum 24 AWG) with
shield, 120 ohm, 23 pf for communication. The default speed of this port is 38.4 Kbps
but it can be upgraded to 115.2 Kbps.
The 485+ (A) is the positive side of the transmit and receive differential signal, the
485– (B) is the negative side. The COM or common is the signal ground. The RS-485
COM signal is connected on the NetAXS controller but not on the NetAXS-123
controllers.
Note:
This signal (RS-485 COM) must NOT be connected to chassis GND.
When daisy-chaining 485 ports together connect the 485+ (A) wires from the
upstream and downstream boards to the 485+ (A) terminal and likewise, connect the
485– (B) wires from the upstream and downstream boards to the 485– (B) terminal.
Using twisted pair for RS-485 communication wiring, use the first
pair as your data
pair, observing polarity. Twist the second pair together and use as the common.
See Figure B-1 on page 79 for reference.
Note:
The common is not used on NetAXS-123 controllers. Connect the external drain
shield to the appropriate earth ground on one end
.
Figure B-1: Twisted Pair