Mitsubishi Electric MELSEC-L Series - Page 197

195
CHAPTER 14 OTHER FUNCTIONS
14
14.7 Alive Check Function
(3) If a response message cannot be received from the connected device
If a response message cannot be received from the connected device (or if an error has been detected) using the
alive check function, the following processes are performed.
• The corresponding connection will be forcibly closed. (The line is disconnected.) Open the connection using
a user program again.
• Open completion signal is turned off, and the error code (C035
H
) is stored in the open error code storage
area.
Ex.
Assuming that the values
*1
are set so that the number of retries may be three, the E71 performs an alive
check at the timing shown in the figure below (an example of alive check using the PING command).
*1 The values of the number of retries and timers can be changed in the initial setting. ( Page 311, Appendix 4.1)
E71
Open completion signal
(address: 5000
H)
Interval timer
value for alive
check of the
target device
Interval timer
value for alive
check of the
target device
The last
communications
Alive check
(1st time)
Starting interval
timer for alive check
of the target device
Interval timer
value for alive
check of the
target device
Alive check
Interval timer
value for alive
check of the
target device
Alive check
resent
(2nd time)
Alive check
resent
(3rd time)
RST sending
(TCP only)
Connection
forced close
(error code: C035
H)