Siemens SIMATIC S7-400 Reference Manual page 198

Analog modules
5.7 Conversion, cycle, settling and response time of analog modules
Conversion time of the analog output channels
The conversion time of the analog output channels includes the transfer of digitized output
values from internal memory, and their digital-to-analog conversion.
Cycle time of analog output channels
The analog output channels are converted sequentially - that is the analog output channels
are converted one after the other.
The cycle time - that is the time expiring until an analog output value is converted again, is
equivalent to the accumulated conversion times of all activated analog output channels. Refer
to the figure "Cycle Time of an Analog Input/Output Channel".
Basic execution time of the analog output channels
The basic execution time corresponds to the cycle time for all the enabled channels.
Note
You should disable any analog channels that are not being used to reduce the scan time in
STEP 7.
Overview of the settling time and response time of the analog output modules
t
1
Figure 5-4
t = Response time
A
t = Setting time
S
t = Specified output value reached
3
t = Output value transferred and converted
2
t = Cycle time, corresponds to n x conversion time (n = activated channels)
C
t = New output value is present
1
Settling time
The settling time (t
specified value is obtained at the analog output - depends on the load. We therefore distinguish
between resistive, capacitive and inductive load.
For information on settling times as a function of load at the various analog output modules,
refer to the specifications of the relevant module.
198
t
A
t
E
t
Z
t
t
2
3
Settling and response times of the analog output channels
to t ) - that is the time from the application of the converted value until the
2 3
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08