How Data Is Read From A Connected Device; How A Connected Device Writes Data - Mitsubishi Electric MELSEC-L SERIES Basic User Manual

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