Keri Systems SB-293 - Manual (Page 55)

Keri Systems, Inc. Technical Reference Manual – PXL-250 and SB-293
Revision 5.5 P/N: 01836-004 Page 55
9.9 TB-1 – RS-485 Controller Network Connection
All PXL-250 controllers communicate, controller-to-controller, through an RS-485
serial communication network. Up to 128 controllers can be attached to this network.
Refer to the RS-485 Networking section on page 28 for information regarding network
cable routing.
To provide the best operating conditions for the RS-485 communication network, the
PXL-250 controller automatically ties the network shield to earth ground at one point,
preventing ground loops.
Refer to Table 14 and Figure 9-13 on page 56 and make the following connections to
attach a network communication line.
NOTE: Do NOT connect earth ground to the network cable shield. The PXL-250
controller automatically connects earth ground to the shield at one point on the
network. This single connection minimizes the effects of ground loops that can affect
controller performance.
NOTE: Keri Systems has identified specific extended network configurations that can
be used to wire a controller network communication bus (subject to certain
limitations). These configurations include a "star" pattern network communication
bus, a spur cable length of up to 5,000 feet, and a total network cable length of up to
16,000 feet. Refer to Addendum 3, PXL-250 Network Wiring Application Note (P/N
01824-002), for detailed information on extended network configurations.
Table 14: RS-485 Network
Communication Connections
TB-1 Description
Pin 1 Tx/Rx Negative
Pin 2 Tx/Rx Positive
Pin 3 Network Cable Shield