GE GFK-0787B user manual Busses and Bus Controllers, Additional Bus Controllers for Communications

1

Busses and Bus Controllers

In a GMR system, there can be one to three bus controllers per bus, per PLC. Larger systems may require more than one I/O subsystem. For example, the GMR system represented below has two I/O subsystems for a total of six independent Genius busses and 18 bus controllers.

PLC A PLC B PLC C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Bus A

I/O Sub±

Bus B

Bus C

system

Bus A

I/O Sub±

Bus B

system

Bus C

Each Genius bus uses a single twinax cable over distances of up to 7500 feet and data rates of up to 153.6K baud.

Each PLC may have up to 31 Genius bus controllers, in multiple racks.

Additional Bus Controllers for Communications

The Genius busses that support GMR input/output groups are also used for internal communications between PLCs, as explained on the previous page. They should not be used for datagram communications. Separate busses for communications can be used for datagrams or additional global data in the application program.

The Bus baud rate should be selected on the basis of the calculations in the Genius I/O System and Communications User's Manual (GFK-90486). For correct autotesting in a GMR system, the Genius bus scan time should not be be more than 60mS.

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	User's Manual ± March 1995