Mitsubishi Electric MELSEC-L SERIES Basic User Manual page 316

• When a communication failure occurs due to a problem such as noise, change the value so that the number
of retries may increase. The number of retries is obtained using the following formula. (When using the
default values, 3 = (60  20))
Number of retries = TCP ULP timer value TCP resend timer value
When the number of retries is three and data sending fails, a data sending error occurs at the timing
Ex.
shown in the figure below (in communications using the fixed buffer).
BUFSND instruction
BUFSND instruction
Completion device + 1
• When not performing the above retry process (set 0 times), configure the setting so that the following
formula is met.
314
Data
command
A
TCP ULP timeout value
A: TCP resend timer value
(The time at which data are sent when ACK is not returned after data transmission)
TCP ULP
=
timer value
(Set the same value for the timer values.)
E71
1st retry 2nd retry
A A
TCP end TCP resend
=
timer value timer value
1 scan
3nd retry