Cyclic Transmission Punctuality Assurance - Mitsubishi Electric MELSEC Q Series Reference Manual

4.1.6

Cyclic transmission punctuality assurance

This function keeps the link scan time constant by making each station to send the specified number of transient
transmissions within one link scan.
● Use this function to eliminate the fluctuation in link scan time, which is caused by transient transmissions. (Optimum
cyclic transmissions are available.)
Note that, if the network line status is unreliable, the cyclic transmission punctuality may not be ensured.
● To keep the link scan time constant even if the network line status is unreliable, use the constant link scan function.
( Page 82, Section 4.1.7)
● While this function is used to keep the link scan time constant, the transmission delay time is not kept constant by this
function.
The transmission delay time is affected by a factor such as a prolonged sequence scan time.
● If the punctuality assurance setting is enabled, the link scan time is constant but longer than the case of no punctuality.
(1) When the punctuality assurance setting is disabled
If each of stations sends transient data several times in one link scan, the link scan time fluctuates and the
punctuality of cyclic transmission cannot be ensured.
Control station
No.1
Link scan time
Hardly affects the link scan time.
Link scan time
The transient transmissions change the link scan time.
80
Normal station
No.2
<When no or a few transient transmissions are sent among stations during one link scan>
<When many transient transmissions are sent among stations during one link scan>
Normal station Normal station
No.3 No.4
Cyclic transmission
Transient transmission