Mitsubishi Electric MELSEC-L Series - How Data Is Read from a Connected Device; How a Connected Device Writes Data

156
13.2.1 How data is read from a connected device
The following figure shows how an E71 sends data in response to a read request sent from a connected device.
13.2.2 How a connected device writes data
The following figure shows how a connected device writes data to the E71 random access buffer.
Write data in the random access buffer of the E71 using the TO instruction.
Asynchronously with the process above, the connected device sends a read request to the E71. (The
E71 side: command receiving)
Upon receiving the read request from the connected device, the E71 sends the data written in the random
access buffer to the connected device that sent the read request. (The E71 side: response sending)
The connected device writes data to the random access buffer of the E71. (The E71 side: command
receiving)
The E71 processes the write request from the connected device and returns the writing result to the
connected device that sent the write request. (The E71 side: response sending)
Asynchronously with the processes and above, the data written in the random access buffer is read
using the FROM instruction.
1
2
3
Connected device
Random access
buffer
CPU module
E71
Writing using
the TO instruction
Read request (command)
Response/data read
ACK (TCP only)
ACK (TCP only)
1
2
1
3
1
2
3
Connected device
Random access
buffer
CPU module
E71
Reading using
the FROM instruction
Writing data (command)
Response
ACK (TCP only)
ACK (TCP only)
1
2
3
1
2