GE GFK-1541B manual Each Modbus channel has a dedicated status bit

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(Status Bit 8) AAUI (90-30) Fuse Blown: This bit is set to 1 when a network port fuse is blown. Otherwise, it is set to zero. This failure is also reported to the PLC Fault Table as “LAN interface hardware failure; switched off network”.

Operation on other ports is not affected. This problem can be caused by a defective transceiver, shorted network or transceiver cable, or a defective Ethernet Interface. The fuse is not field- replacable so the module must be returned to GE Fanuc for repair.

(Status Bit 9) Any SRTP Channel Error: This bit is set to 1 if there is presently an error on any of the established SRTP channels; i.e., if the individual Channel Error bit is set for any SRTP channel. This bit is not used by Modbus Channels.

(Status Bit 13) LAN OK: This input will be held at the value 1 as long as the Ethernet Interface software is able to communicate on the network. If the network should become inaccessible from this Interface, due either to local or network problems, this bit will be set to 0. If LAN communication becomes possible, it is set to 1.

(Status Bit 14) Resource Problem: This input is set to 1 whenever the Ethernet Interface software experiences a resource problem (i.e., lack of data memory). The bit is reset to 0 on a subsequent PLC sweep. The Ethernet Interface may or may not be able to continue functioning, depending on the severity of the problem. Use the PLC Fault Table to understand the problem. See “Troubleshooting”, for further information. In addition, you can use the Station Manager STAT B and LOG commands to further understand the problem.

(Status Bit 16) LAN Interface OK Bit: This input is set to 1 by the Ethernet Interface each PLC scan. If the Ethernet Interface cannot access the PLC, the CPU will set this bit to 0. When this bit is 0, all other Ethernet Interface Status bits are invalid.

Each Modbus channel has a dedicated status bit:

(Status Bits 17, 19, 21 ... 79) Connection Open Bit: This bit is 1 when a TCP connection exists for the associated channel. The bit is 0 when the connection does not exist (either never created or has disconnected for some reason). The bit is also set to zero when the PLC goes to STOP, because all connections are automatically closed upon STOP transition.

(Status Bits 18, 20, 22 ... 80) Reserved: When a Channel is in use as an SRTP Channel, these bits are not used.

Note

For Series 90-30 PLCs, bits 49-80 are reserved for future use.

4-22 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B