Emerson EZMotion User Manual page 109

Number of Capture Units
This parameter defines the number of Capture objects available. Maximum is eight.
Name
You can assign a descriptive name to each capture, making the configuration easier to follow. The length of the text string is
limited by the column width with a maximum of 12 characters.
Simply double click on the Name field of any capture line, enter the descriptive name and then enter, to assign a name to it.
Capture Parameters
The following four parameters are the data that is acquired by the position capture object. These parameters are available to
be used as variables in a program. The four parameters can be accessed as follows:
Capture.#.CapturedTime - The time, in microseconds, from a free-running 32-bit binary counter at which the CaptureActivate
signal activated.
Capture.#.CapturedPositionCommand - The command position, in user units, at the time when the CaptureActivate signal
activated.
Capture.#.CapturedPositionFeedback - The feedback position, in user units, at the time when the CaptureActivate signal
activated.
Capture.#.CapturedMasterPostion - The master axis feedback position, in master axis distance units, at the time when the
CaptureActivate signal activated.
The captured data remains in these parameters until the capture component is reset and CaptureActivate is activated the next
time. When the capture component is reset and CaptureActivate is activated, the data related to the previous capture will be
over-written by the most recent capture data.
Capture Sources and Destinations
Figure 97 shows a block diagram of the Capture object
Figure 97:
Sources
CaptureTriggered - The CaptureTriggered signal is read-only and indicates that the Capture component was activated, and
that data has been captured. CaptureTriggered will activate on the leading edge of CaptureActivate if the Capture component
is enabled and reset. Capture Triggered will remain active until CaptureReset is activated.
Destinations
CaptureEnable - The CaptureEnable is used to enable or "arm" the capture component. If the CaptureEnable is not active,
then the CaptureActivate has no effect, and the CaptureTriggered remains inactive. Once the CaptureEnable is activated, the
Capture component is ready and waiting for a CaptureActivate signal to capture data. CaptureEnable is a read-only
destination on the Assignments view, and is accessible through a user program.
CaptureActivate - If the Capture component is enable and has been reset (CaptureTriggered is inactive), then the rising edge
of CaptureActivate will capture the four data parameters and cause CaptureTriggered to be activated. If the Capture
component is not enabled, or has not been reset, the CaptureActivate will be ignored.
CaptureReset - The CaptureReset is used to reset or re-arm the capture component after it has been activated.
Once the capture has been activated, the CaptureTriggered destination will be active. The capture component cannot capture
data again until it has been reset. The capture component will automatically reset itself if the CaptureEnable signal is removed.
Figure 98:
Figure 98 is a timing diagram that shows how the different capture related sources and destinations function. The three
EZMotion User/Programming Guide
Revision A8
CaptureEnable
CaptureActivate
CaptureReset
Capture Object
CaptureEnable
CaptureActivate
CaptureTriggered
CaptureReset
Capture Timing Diagram
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Time
CaptureTriggered
Command Position
Feedback Position
Master Position
Captured Data
1
3
2
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