Mitsubishi Electric LE7-40GU, Instruction Manual, Page: 70 / 154

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5 MODBUS/TCP (SLAVE)
5.2 Communication Setting
Access by request command
For any access to data in LE7-40GU from the master station, data can be read and written by handshake between the
"request command execution (RY2F)" flag and the "request command completion (RX2F)" flag.
This access is performed using a 2-word word device of the master station.
This 2-word data is comprised of the request command, to which the upper 4 bits of the first word are assigned, and the
request code, to which the lower 12 bits are assigned, and the setting data, to which the next word is assigned.
There are three types of request command, Data Monitor, Writing to RAM, and Writing to RAM + ROM, according to the
selection of data reading and writing method.
In the ROM for storage against power interruption, the allowable number of times of writing is limited. Accordingly, data
cyclically written and updated by the PLC must be written only to the RAM.
The request code is the data number (address) of the data that executes the request command. The subsequent data setting
is the data to be written to the data number, and if the request command is the monitor, the data setting data is ignored.
When double word data is written to send data in the master station, and the handshake is executed by turning ON/OFF the
request command execution flag and request command completion flag as follows, LE-70GU sends back the request
command execution request.
1.
The master station is set to request command execution ON.
2.
LE7-40GU executes processing when receiving turning ON of the request command execution by the master station.
3.
LE7-40GU turns ON the request command completion.
4.
The master station receives the request command completion ON.
5.
The master station is set to request command execution OFF.
6.
LE7-40GU receives turning OFF of the request command execution by the master station.
7.
LE7-40GU turns OFF the request command completion.
8.
The master station receives the request command completion OFF.
Please perform reading of the execution results of the request command between step 4 and 5 of the handshake procedure.
If an error occurs, in the execution result with respect to the request command from the master station, turn on the network
alarm occurrence flag and output the device number where the alarm occurred to the network alarm device number monitor.
For the request command execution result, refer to the following.
 LE7-CCL APPLICATION MANUAL
bit 15 to 12 bit 11 to 0
Request command Request code
Setting data
Monitor Writing to RAM Writing to RAM + ROM
Writing data is reflected in the settings based on a
data read request from the master station but is
not stored in the case of a power failure. Writing data is reflected in the settings based on a
data write request from the master station but is
not stored in the case of a power failure. Perform the above RAM write + data power failure
write.
Request command Contents of execution Execution result
H0 Monitor Monitored value
H1 Writing to RAM Writing result
H2 Writing to RAM + ROM Writing result