Toshiba V Series User Manual page 136

Chapter 6 Socket Interface Communication
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• The remote node may have gone down.
• Power may have been lost.
• The remote and local nodes may have become disconnected from the network.
• ACK transmission timing in the EN311 TCP socket
When reception data in the EN311 is read out by a receive request from the S
controller, the EN311 sends an ACK (acknowledge response) to the node that sent the
data. Note that the EN311 will send an ACK every second to the source node even if it
does not issue the TCP receive request. However, if it does not issue the TCP receive
request, the data reached to the destination socket will be stored in the TCP receive
buffer. The receive buffer on the TCP socket has the limit of 5840 bytes per packet.
The data should be received by the TCP receive request.
• With TCP receive requests, the amount of data transferred to the reception data
storage register area will differ with both the timing with which the S controller issued
the receive request and the timing with which the data arrives at the EN311.
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 detecting the end mark
included in the transmitted data) and iterate receive requests.
• User programs must save all incoming data so that the register area used to transfer
data to the S controller is not overwritten when using iterated receive requests.
• The EN311 uses a priority ordering in processing sockets 1 through 8. Therefore,
systems constructed so that socket 1 is activated frequently may not be able to
process socket 8, resulting in the following error response:
Error status: Send completion timeout ••• 5002(16#EC76)
When constructing a system, take the socket utilization conditions into account when
allocating sockets. Since the send/receive processing for each socket requires about
50 ms, applications that issue send or receive requests to a given socket should leave
an interval of at least 50 ms times the number of sockets used between each request.
Interval between send (receive)requests to the same socket >= Number of
sockets used ¥ 50 ms
Similarly, the above intervals averaging 50 ms should be left between transmissions
from remote nodes to the local node.
Interval between remote node transmissions >= Number of remote nodes ¥ 50
ms
Ethernet module User's Manual