205
APPENDICES
A
Appendix 4 Specificat
ions Co
mpar
ison w
ith Ether
net Module
(2) Differences on MC protocol functions between the Built-in Ethernet port QCPU
and Ethernet module
*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.
(
Item
QJ71E71-100
Built-in Ethernet port
QCPU
Consequence of a
communication with the
Built-in Ethernet port QCPU
Action
Data sending method on TCP when the
response message size exceeds 1460
bytes
(TCP Maximum Segment Size Option
transmission)
Data sending method is
selectable.
(Default: "Disable TCP
Maximum Segment
Size Option
transmission")
Data sending method is
fixed to "Enable TCP
Maximum Segment Size
Option transmission" and
cannot be changed.
If the response message size
exceeds 1460 bytes, the message
split by the external device may not
be read correctly.
Perform the
procedure described
in Page 60, Section
5.1.3 (6) so that the
external device can
process split data.
Wait time for receiving entire message
(from the first message to the last
message) when a request message is
split and sent
1 to 16383.5 seconds.
(Default: 30 seconds)
(The time value can be
changed in "Response
monitoring timer" under
"Timer setting" of GX
Developer.)
Fixed to one second.
(A request message is
discarded if the next part
of the split message
cannot be received within
one second.)
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.
Retry
communication from
the external device.
If a communication
timeout frequently
occurs, reduce the
load of the external
device or Ethernet
network.
Operation when request messages are
consecutively sent to one connection
Even when one
connection
consecutively receives
request messages,
each request message
can be processed.
When one connection
receives another request
message before
responding a request
message, the second
message is discarded.
*1
If request messages are
consecutively sent to one
connection, response messages
are not returned and a
communication timeout may occur
in the external device.
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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