Termination Requirement For Expansion Or Remote System; Powering Down Individual Expansion Or Remote Baseplates; Series 90-30 Plc Backplane - GE 90-30 PLC Series Installation And Hardware Manual

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Termination Requirement for Expansion or Remote System

When two or more baseplates are connected via the I/O Bus Expansion System, the I/O Expansion
Bus must be properly terminated. The most common method of terminating the I/O Expansion
Bus is by installing a termination resistor pack (IC693ACC307) on the open connector on the last
(most distant from the CPU) Expansion or Remote baseplate in the system. The resistor pack is
physically mounted inside of a connector. Although a termination resistor pack is shipped with
each baseplate, only the last baseplate in the chain needs to have this termination connector
installed. Unused termination packs can be discarded. The prewired 50 foot (15 meter) cable
(IC693CBL302) has termination resistors wired inside the connector on one end of the cable. This
cable can be used if only one expansion rack is needed in a system and a 50 foot cable link is
required (the IC693ACC307 resistor pack is not needed in this case). Also, a custom-built cable
with built-in resistors would eliminate the need for the IC693ACC307 resistor pack.

Powering Down Individual Expansion or Remote Baseplates

Expansion or Remote baseplates can be powered-down individually without affecting the operation
of other baseplates; however, powering off a baseplate generates a loss of module
(LOSS_OF_MODULE) fault in the PLC Fault Table for each module in the baseplate. When this
fault condition occurs, and until the baseplate is powered back on and all modules recovered, the
lost I/O modules are not scanned. For more information on the power-up and power-down
sequence, see Chapter 2 in the Series 90-30 Programmable Controller Reference Manual,
GFK-0467.

Series 90-30 PLC Backplane

The Series 90-30 PLC backplane (on all three types of baseplates) has a dedicated I/O
communications bus. The signals on the remote baseplate backplane are optically coupled and an
isolated DC-DC power supply converter is provided to isolate the signals from other backplanes.
3-12 Series 90-30 PLC Installation and Hardware Manual – August 2002
Power bus - connects the power supply outputs to the modules in the baseplate.
I/O Communications bus - the CPU communicates with I/O modules over this bus. This bus
is connected to the I/O busses in Expansion and Remote racks via the I/O Bus Expansion
connectors and cables.
Special Intelligent Module bus - exists only on a CPU baseplate; therefore, certain special
intelligent option modules, such as the Programmable Coprocessor Module (PCM) ,
Alphanumeric Display Coprocessor (ADC), and CMM (Communications Control Module –
IC693CMM311), only work in a CPU baseplate.
GFK-0356Q