FX3U-ENET-L USER'S MANUAL - Automation Systems and Controls

5COMMUNICATION PROCEDUREMELSEC-F(3) When communication errors occur, the setting value should be changed toincrease the number of retries.The number of retries is obtained by using the following equation:(In case of the initial values, 2 = (60/20) - 1)•Numberof retriesTCP ULP timer valueTCP resend timer value-1Example: Assuming the values are set in such a way that the number of retries istwo, a data transmission error will occur at the timing shown in thefigure below if data transmission fails (when communicating using fixedbuffer).Transmission requestand status#1610, #1611W0001HR0002HR0008HDatacommandEthernet moduleFirst retrySecond retryA A ATCP ULPtimer value=TCP endTCP ULP timeoutTCP resendvalue=timer value timer valueA (Each : TCP timer resend value timer should valuebe identical.)(The time after which the data should be retransmitted whenan "ACK" is not returned after sending data.)(4) Perform the following setting in order to eliminate the retries explained in (3) (i.e.,to set the number of retries to 0).•TCP ULPtimer value=TCP endtimer value(Each timer value should be identical.)=TCP resendtimer value(5) The target existence check is a function whereby the Ethernet module checkswhether or not a remote device is functioning normally by sending an existencecheck message and then waiting to see whether a response message isreceived. It is used if a connection to a remote device is open but communicationwith the remote device has not been performed for a certain period of time.(a) The existence check function has two methods of checking: PING andKeepAlive.The Ethernet module performs each of the existence checks based on thesetting values explained in (7) to (9) of this section and the existence checksetting of the open settings (refer to Section 5.5 (6)).The existence check function (Ping or KeepAlive) can be selected at the timeof operation setting or re-initialization.For the operation setting, refer to Section 4.6.Refer to Subsection 5.2.3 for the explanation on re-initialization.5 - 85 - 8