Mitsubishi Electric Q03UDVCPU User Manual page 207

(2) Differences on MC protocol functions between the Built-in Ethernet port QCPU
and Ethernet module
Item
Data sending method on TCP when the
response message size exceeds 1460
bytes
(TCP Maximum Segment Size Option
transmission)
Wait time for receiving entire message
(from the first message to the last
message) when a request message is
split and sent
Operation when request messages are
consecutively sent to one connection
*1 When the 4E frame is used in the High-speed Universal model QCPU with serial number (first five digits) of "18052",
even if one connection consecutively receives request messages, each request message can be processed.
( Page 61, Section 5.1.3 (7))
Built-in Ethernet port
QJ71E71-100
Data sending method is
Data sending method is
selectable.
fixed to "Enable TCP
(Default: "Disable TCP
Maximum Segment Size
Maximum Segment
Option transmission" and
Size Option
cannot be changed.
transmission")
1 to 16383.5 seconds.
Fixed to one second.
(Default: 30 seconds)
(A request message is
(The time value can be
discarded if the next part
changed in "Response
of the split message
monitoring timer" under
cannot be received within
"Timer setting" of GX
one second.)
Developer.)
When one connection
Even when one
receives another request
connection
message before
consecutively receives
responding a request
request messages,
message, the second
each request message
can be processed.
message is discarded.
Consequence of a
communication with the
QCPU
Built-in Ethernet port QCPU
If the response message size
exceeds 1460 bytes, the message
split by the external device may not
be read correctly.
If each part of the split request
message is not sent within one
second, a response message is
not returned and a communication
timeout occurs in the external
device.
If request messages are
consecutively sent to one
connection, response messages
are not returned and a
communication timeout may occur
*1
in the external device.
APPENDICES
Action
Perform the
procedure described
in Page 60, Section
5.1.3 (6) so that the
external device can
process split data.
Retry
communication from
the external device.
If a communication
timeout frequently
occurs, reduce the
A
load of the external
device or Ethernet
network.
Check that the
external device
receives a response
message before
sending next
request message.
(Do not
consecutively send
request messages
from the external
device.)
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