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Performance
(
continued)
Modbus messaging service response time
Global Data service response time
Modicon Premium automation
platform
Ethernet Modbus/TCP network
Performance
Application response time
Modbus (or Uni-TE) messaging service response time
Exchanges between the PLC processor and the Ethernet module are synchronous
with the PLC scan cycle time (CT), in the same way as the I/O exchanges. When an
event occurs (such as an input being set to 1 for example), a message can be
transmitted only after this input has been taken into account (start of the next cycle)
and the PLC (Modicon M340, Modicon Premium or Modicon Quantum) program has
been executed, i.e. on average approximately 1.5 cycles after the event has occurred.
The network access time (NAT) shown in the table below in ms is a total of the
module transit time and the delay before the message can be transmitted on the
network.
Processing of
Modbus TCP/IP
message requests
Modicon M340
Modicon Premium
Modicon Quantum
BMX NOE 0100
BMX NOE 0110
BMX NOC 0401
BMX NOR 0200H
BMX P34 2020
BMX P34 20302
TSX ETY 110WS TSX ETY 4103/5103
TSX WMY 100
TSX P57 10...60
TSX ETC 101
140
NOE 771 00/10
140
NOE 771 01/11
140
NWM 100 00
140
NOC 771 01
140
CPU 651 50/60
140
CPU 652 60
Network access time
(
NAT)
< 10 ms
< 10 ms
< 25 ms
< 10 ms
< 10 ms
< 10 ms
The transaction time TT includes the delay between the transmission of a message
from a client station
1
,
its reception by the server station
2
,
processing of the request,
sending back the response and it being taken into account by the station
1
(
updating
of an output for example).
As the above block diagram shows:
b
The transaction time TT will be between:
2
x
CT1
+
2
x
NAT < TT < 4
x
CT1
+
CT2
+
2
x
NAT
b
The average duration TT
av
is equivalent to:
TT
av
= 3
x
CT1
+
0.5
x
CT2
+
2
x
NAT
Global Data service response time
The transaction time TT includes the delay between publication of Global Data by
the station
1
,
its reception and processing by the remote station
2
and its
retransmission to the initial station
1
:
For an exchanged variable:
b
If CT < 5 ms,
transaction time:
TT = 5 to 6
x
CT
b
If CT
u
10
ms,
transaction time:
TT = 3
x
CT
Station 1
Event
CT1
NAT
NAT
CT2 CT2
Station 2
Report
TT
CT1
CT1 CT1
Action
Station 1
Synchro pulse
CT
CT CT
NAT
NAT
CT CT
Station 2
Synchro
feedback
TT
Transaction time
Publication
Publication
Subscription
2
1
3
4
5
6
7
8
9
10