Data Sending Procedure - Mitsubishi Electric MELSEC-L SERIES Basic User Manual

12.3

Data Sending Procedure

This section describes how an E71 sends data to the connected device.
(1) Procedure exists
The following is the data send process performed in the fixed buffer number 1 area for the connection number 1.
Initial normal completion
signal X19
Open completion signal
(address: 5000
BUFSND instruction
BUFSND instruction
completion device
BUFSND instruction
completion device + 1
Confirm the normal completion of the initial process. (Initial normal completion signal (X19): ON)
1
Establish a connection between the E71 and the connected device and confirm the normal completion of the
2
open process of the connection number 1.
Execute the BUFSND instruction. (The data is sent.)
3
The send data in the fixed buffer number 1 is sent to the connected device by the send data length.
4
When the connected device receives the data from the E71, the connected device sends a response to the
5
E71.
When the E71 receives the response from the connected device, the E71 stops sending data. If a response is
6
not sent within the response monitoring timer value, a data send error occurs.
After the data send process abnormally ends, execute the BUFSND instruction again to repeat the send
process.
*1 Refer to the section describing the initial setting when adjusting the monitoring timer value. (
4.1)
● The items configured in the open setting become enabled when Open completion signal of an E71 is started up.
● Do not send data (command) before data communications are completed (or a response is received) in response to the
previous data (command).
● When an E71 communicates data with multiple connected devices, data can be sent sequentially; however, switching the
connected devices before sending/receiving data is recommended to prevent communication problems. When a
connection opened using the UDP/IP protocol is used, change the setting values in the communication address setting
area before sending or receiving data to switch the connected devices.
Initial process Open process
1
2
[b0])
H
CHAPTER 12 COMMUNICATIONS USING A FIXED BUFFER
Sending data Receiving a response
3
ACK
(TCP only)
4 5
*1
6
1 scan
ACK
(TCP only)
Page 311, Appendix
123
12