Technical information

3/16
Modicon M580 automation
platform
Ethernet Modbus/TCP network
Performance
Application response time (continued)
I/O Scanning service response time
The response time RT includes the time between taking account of information from
a remote input and updating the state of a remote output. It includes the processing
time in the PLC.
This response time RT consists of the following parameters:
v TMod In and TMod Out: Response time of the read/written device, excluding the
electrical transition time at the input/output (TMod depends on the device, usually
between 1 and 8 ms)
v TIOS In and TIOS Out: Time between 2 read/write operations on the same device
(0.3 ms
x number of devices scanned), at least equivalent to the congured scan
time
As TIOS is executed in parallel with the PLC cycle, it can be hidden from the
viewpoint of the response time RT.
v Cycle T: PLC scan cycle time
v TNet: Propagation time on the network (depends on the application, but usually
TNet = 0.05 ms at 10 Mbps and 0.005 ms at 100 Mbps)
The response time RT can be estimated using the following 3 formulae:
b RT
min
, minimum response time with TIOS hidden and 1 PLC scan cycle:
b RT
typic
, typical response time with 0.5 TIOS hidden:
b RT
max
, maximum response time with TIOS not hidden:
RT
min
= (TMod In + 0) x TIOS In + (Tnet + N) x cycle T + (0 x TIOS Out) + Tnet + TMod Out
RT
typic
= (TMod In + 0.5) x TIOS In + (Tnet + N) x cycle T + (0.5 x TIOS Out) + Tnet + TMod Out
RT
max
= TMod In + TIOS In + (Tnet + N) x T cycle + TIOS Out + Tnet + TMod Out
Performance (continued)
I/O Scanning service response time
Device 1
Device 2
Manager
Hub
Input
Output
CT
RT
Ethernet Modbus/TCP
Response time (RT)
Input
Output
TMod In
TMod Out
TIOS In
TNet
N x Cycle T
TIOS Out
TNet
Processors:
page 1/18
I/O architectures:
page 2/2
Software:
page 4/2
Ruggedized Modicon M580
modules: page 5/2
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