Mitsubishi Electric QJ71E71-100 User Manual page 229

(c) When data is sent from the connected device
• When using the "Procedure exist" method
If a response timeout to the E71 occurs, change the connection destination to the other system and send the
data.
• When using the "No procedure" method
Send the same data to both the control system and standby system.
The following shows an example of the sending procedure for sending data to a redundant system using the
"Procedure exist" method.
Fixed buffer communication procedure
(Procedure exist)
Data is sent to the system A.
Did a timeout occur?
NO
A response is received from
the system A.
Take care of the following when performing a resend process at system switching.
• When performing communications while synchronizing sending and receiving, system switching may occur during
the communications, and the system may be switched with the sending and receiving not synchronized. To
perform system switching, restart communications after initializing the synchronization for safety.
• After executing the WRITE instruction, execute it again because it is difficult to determine that the instruction has
been completed. However, note that the same instruction may be executed twice.
(5) Communicating using a random access buffer
The buffer memory of the E71 is not tracked. Therefore, when writing data to the random access buffer, write the
same data to the control system and standby system.
YES
Data is sent to the system B.
Did a timeout occur?
NO
A response from the system B
is received.
CHAPTER 14 OTHER FUNCTIONS
YES
An error has occurred.
14
227