Innotech Genesis V4 System - Manual (Page 86)

Installation Instructions for Innotech Genesis Systems
Edition 011100
A-5
A-4.2. GENESIS COMMS WIRING CONSIDERATIONS. The maximum
number of nodes or devices that can be connected on one section of Comms cable is 32. This
limit is set by the characteristics of the RS485 ICs.
The maximum length of Comms cable is 1000 metres. This is determined by the
characteristics of the RS485 ICs and by the characteristics of the cable. In practice, the
maximum length of cable is determined by the quality of the signals. The signal will be
degraded by using cable which does not meet the RS485 cable specification and by installing
the cable in locations where it is subject to interference from other cables and equipment. In
severe cases, it may not be possible to have 32 nodes on one section of cable.
A node is any Genesis product with an RS485 connection. These devices are listed in
Paragraph A-2.
To increase the total number of nodes on a system, a GENII RPTR Repeater Module must be
used (Figure A-5). The two ports on a Repeater Module reside on different sections of the
system and each section can have up to the maximum of 32 nodes. With one repeater, a total
of 62 nodes can be connected on the system. A repeater can be connected at any point on the
network providing bus topology is maintained.
Figure A-5. Network Nodes Considerations.
A-4.2.1. Genesis Comms Wiring Connections. Figure A-6 illustrates the
arrangements for connecting the data conductors and screen for the Comms cable to
Genesis products.
It is most important that the two conductors of a twisted pair be correctly identified. Take
extra care with cable that has two twisted pairs with only an overall screen. If a conductor
from one twisted pair is “paired” with a conductor from the other twisted pair, the two data
streams will interfere with each other. This may cause complete failure of the RS485
communications.
1 2 3 4
- - -
29 30 31 32
Port 2 of the Repeater is one of the 32 nodes on this network
Port 1 of the Repeater is one of the 32 nodes on this network
1 2 3 4 - - - 29 30 31 32
1 2 3 4 - - - - 29 30 31 32
1
2