Status Data; Types Of Status Data - GE RX3i User Manual

Status Data

9.4
This section describes all the status data that is available to the ladder program to determine the state of the
Ethernet interface and its Modbus/TCP channels.

Types of Status Data

There are three main types of status data available to the application program:
▪
Ethernet Interface status bits,
▪
FT Output of the COMMREQ function block
▪
COMMREQ Status Word
Ethernet Interface Status Bits
The status bits are updated in the CPU once each PLC scan by the Ethernet interface. These bits are generally
used to prevent initiation of a COMMREQ function when certain errors occur or to signal a problem on an
established channel. The status bits include the LAN Interface Status bits and the Channel Status bits. The
starting location of these bits is set up when the module is configured.
The LAN Interface Status bits monitor the health of the Ethernet interface itself, such as the LAN Interface OK
bit. The Channel Status bits monitor the health of a channel. Each Modbus channel has a dedicated status bit.
For details of the status bits and their operation, refer to "Monitoring the Ethernet Interface Status Bits" in
Chapter 12, "Diagnostics."
FT Output of the COMMREQ Function Block
This output is set if there is a programming error in the COMMREQ Function Block itself, if the rack and slot
specified in the COMMREQ SYSID parameter is not configured to contain an Ethernet interface, or if the data
block length specified in the Command Block is out of range. This output also may indicate that no more
COMMREQ functions can be initiated in the ladder program until the Ethernet interface has time to process
some of the pending COMMREQ functions.
If the FT Output is set, the CPU does not transfer the Command Block to the Ethernet interface. In this case, the
other status indicators are not updated for this COMMREQ.
The FT Output passes power upon the following errors:
▪
Invalid rack/slot specified. The module at this rack/slot is unable to receive a COMMREQ.
▪
Invalid Task ID.
▪
Invalid Data Block length (zero or greater than 128).
▪
Too many simultaneous active COMMREQs (overloading either the PLC CPU or the Ethernet interface).
GFK-2224Q January 2017
Chapter 9. Modbus/TCP Client
161