Siemens SIMODRIVE 611U Product Information page 55

Response times for the measuring function
The technology CPU can be used for measuring with different configurations. Depending on
the connection of the axis (using PROFIBUS DP) and the processing level (position control
cycle clock or interpolator cycle clock), you must allow for different response times for the
Measurement function in the application.
The measurement in the user program is controlled by calling the MC_MeasuringInput
function block. You can specify when the measuring function is to be active during the call:
● immediately (without measuring window / triggering range)
● within a position-dependent measuring window
For the Measurement without measuring window, MC_MeasuringInput immediately activates
the measuring input.
A configuration-dependent delay elapses before the measuring edge is evaluated at the
hardware input (refer to the "Measurement without measuring window" table). To be certain
to detect the measuring edge, you must ensure that MC_MeasuringInput is executed earlier
by this amount of runtime in the user program.
When measuring with measuring window, the job is first only registered in the system with
MC_MeasuringInput. The measuring input is activated only when the axis has reached the
start of the measuring window.
A configuration-dependent delay elapses after reaching the start position of the measuring
window on the axis (mechanical construction) before the measuring edge is evaluated at the
hardware input (refer to the "Measurement with measuring window": Measuring edge is
detected in the window" table). To ensure that the measuring input is active when the
required start position of the measuring window is reached, you must move forward the start
of the measuring window depending on the axis speed and the response time when the
function is called.
The same applies to the end of the measuring window. It is important that the measuring
input is no longer active when the end of the measuring window on the axis (mechanical) is
crossed (for the run times, see "Measuring with measuring window: no measuring edge in
the window" table).
These run times can be compensated using the MeasuringRange.activationTime
configuration data ("Measuring input configuration", "Activation time of the triggering range
on the measuring input" figure).
Note
The offset of the measuring window only functions reliably when the axis velocity
• Within the measuring window is constant and
• Known before the function call.
You can determine the response times for your configuration using the following tables. The
values in the tables refer to set system cycle clocks. By using the actual times, you can
calculate the response time in milliseconds.
Connecting the SIMODRIVE 611U to the Technology CPU
Product Information, 03/2008, A5E00272066-05
StartPosition = EndPosition
StartPosition < > EndPosition
Commissioning
4.4 Setting up a STEP 7 project
55