94 Ethernet module User’s Manual
Chapter 6 Socket Interface Communication
6
Figure 6-7 Transmission Data Fragmentation in the TPC socket
(9) When the transmission data is fragmented as discussed above, the amount of data
transferred to the S controller in a TCP socket interface receive request differs
depending both on the timing with which the S controller issues the receive request
and the timing with which the data arrives at the EN311.
(10) To handle single units of transmission data on the receiving side as single units as
well, the user software on the receiving side must recognize the end of the
transferred data (either by using counts in the transmitted data or by including an
end marker in the transmitted data) and iterate receive requests until all the
transmitted data has been received. ("B" does not arrive at the EN311 earlier than
"A" through the TCP/IP processing.)
(11) User programs must store all incoming data so that the register area used to transfer
data to the S controller is not overwritten when using iterated receive requests.
Sending EN311
Transmission line
EN311 Receiving
S controller S controller
(1) Send request (2) (3)
(4) First receive request
2000 bytes 1460 bytes 1460 bytes
2000 bytes
A A
A
1460 bytes
B B
540 bytes 540 bytes
(5) Second receive request
2000 bytes
B
540 bytes
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