Chapter 9 Fieldbus I/O Interfaces
PAGE 9-25
PLC Logic Example: Sending Message data to FEC Master Spindle
The MSG message command initiates the message data to be sent or received. The ‘Write” tag sends the data to the
device connected, and the ‘Read’ tag retrieves the data from the connected device.
In the example above, the Write MSG command takes place at or near the start of the machine cycle before the FEC
controller has been issued a START command. (The FEC HFC Controller, must receive the Write Data before the
cycle START is given (before the cycle is started). Once received, the data is buffered and will be used until new
message data is received or the “ID DATA CLEAR” Input signal is enabled (See Input signals). (The ID data received
by the FEC HFC Controller will be married with the fastening data and will continue to use the same message data it
receives until new data is sent or the ID Data Clear signal is turned on. Care must be taken so data is not recorded with
the same ID data in that case)
The “Read” Tag in the example above is shown happening AFTER the FEC fastening is completed. Once fastening
is completed, the MSG Read command can be performed and the fastening result data will be read into the PLC.
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