Access By Request Command - Mitsubishi Electric LE7-40GU Instruction Manual

Access by request command

For any data access from the master station to the local station, data can be read or written by handshaking between the
"request command execution" flag and the "request command completion" flag.
This access is performed using a 2-word word device of the master station.
In the double word data, the 4 high-order bits of the first word are assigned to the request command and the 12 low-order bits
are assigned to the request code, and the second word is assigned as the word for the set data.
bit 15 to 12
Request command
Setting data
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.
Monitor
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.
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.
Request command
H0
H1
H2
The request code indicates the data No. (address) of data for which the request command is executed. Also, the subsequent
data setting is the data to be written to that data number.
If the request command is a 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, the local station sends back the request
command execution request.
1.
The master station is set to request command execution ON.
2.
The local station processes in accordance with the master station request command execution ON.
3.
The local station is set to request command completion ON.
4.
The master station receives the request command completion ON.
5.
The master station is set to request command execution OFF.
6.
The local station receives the request command execution OFF from the master station.
7.
The local station is set to request command completion OFF.
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, triggered by the request command from the master station, the local station turns ON the network alarm
occurrence flag and outputs the device No. that has the error to the monitor of the device number of the network alarm.
For the request command execution result, refer to the following.
LE7-CCL APPLICATION MANUAL
6 N:N NETWORK
96
6.3 Communication Setting
bit 11 to 0
Request code
Writing to RAM
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.
Contents of execution
Monitor
Writing to RAM
Writing to RAM + ROM
Writing to RAM + ROM
Perform the above RAM write + data power failure
write.
Execution result
Monitored value
Writing result
Writing result