EST3 Installation and Service Manual

System overview

Digital network subsystem

Network data riser wiring

The network data riser provides the communication path between each CPU module (3-CPUx or 3-ANNCPUx) installed in the system. Each CPU module has two bi-directional RS-485 ports (Network A and Network B) that are used to connect the network data riser wiring. Network B is isolated from ground and Network A is not.

The correct method for running the network data riser is to connect the isolated Network B port on one CPU module to the non-isolated Network A port on another. Any remote CPU modules connected to a local CPU module’s Network B port is considered to be downstream from the local CPU module. Any remote CPU modules connected to a local CPU module’s

Network A port is considered upstream from the local CPU module.

Additionally, next and previous refer to the order in which remote CPU modules are electrically connected to a local CPU module. Previous refers to the remote CPU module whose isolated Network B port connects to the local CPU module’s non-isolated Network A port. Next refers to the remote CPU module whose non-isolated Network A port connects to the local

CPU module’s isolated Network B port.

Note:

Since the data traveling the network data riser is bi-directional, out and in references are used to direct wire connections.

Class B network data risers

In a Class B network, a break or short in the network data riser wiring divides the network into separate independent networks.

Panels on the same side of the line fault will communicate with each other but not with panels across the line fault. Figure 1-10 shows the wiring for a Class B network.

1.16 EST3 Installation and Service Manual