En311 Socket Interface Usage Notes; Transmission/Reception Data Handling In Udp Sock; Et Interface - Toshiba V Series User Manual

6.2 EN311 Socket Interface Usage Notes

This section presents the points that require attention when using the socket interface on
the EN311.
6.2.1 Transmission/Reception Data Handling in UDP Socket Interface
(1) In UDP socket interface transmission, data sent in a single transmission is handled
by the receiving EN311 as a single data unit, and that data is transmitted to the S
controller in a batch operation by a receive request.
(2) The size of data units that can be handled by the EN311 socket interface in a single
operation is limited to a maximum of 2000 bytes. If the sending node sends a data
unit larger than 2000 bytes, the EN311 UDP socket interface will not be able to
receive that data. Users should determine the maximum size of the data units to be
sent or received at the system design stage.
(3) Transmitted data that exceeds 1472 bytes is divided (fragmented) into units of 1472
bytes. This is the limit of the length of packets (data units flowing on the network)
transmitted over the transmission line (see Figure 6-8).
For example, when transmitting 2000-byte data, the event shown in Figure 6-5 can
occur.
(a) The sending S controller user program requests a transmission of 2000 bytes.
(b) The transmitted data is divided into two fragments, A (with 1472 bytes) and B
(with 528 bytes).
(c) A and B are put onto the transmission line.
(d) The receiving side EN311 connects the received data A and B, restoring the
original data.
(e) The data is accepted by a receive request from the receiving side S controller for
2000 bytes of data and the data is stored in the specified register (see section
6.4.3, "UDP receive request (using the URECV_T instruction)").
(4) In the UDP socket interface, after the transmitted data is reassembled to the original
data it is passed to the user program and stored in the specified register (the
fragments A and B are reassembled to the original data by UDP/IP processing).
Sending
S controller
(1) Send request
2000 bytes
Figure 6-5 Transmission Data Fragmentation in the UDP Socket Interface
(5) In receive request programs from the S controller, set the size of reception data to a
value equal to or larger than that of the maximum size for the transmission data in a
single operation.
(6) Allocate an area one word larger than the transmitted data size as the S controller
register area that will hold the received data. As the result of a receive request,
information indicating the size of the transmitted data for the single operation plus the
data transmitted in the single operation will be stored in that area.
6F8C0904
EN311 Transmission line
(2) (3)
1472 bytes (A)
A
B
528 bytes (B)
6.2 EN311 Socket Interface Usage Notes
EN311 Receiving
S controller
(5) Receive request
(4) 2000 bytes
A B
Receive / Response
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