mpiMotionModify modifies the parameters of a Motion object (motion) if motion is in progress (MPIStateMOVING). The types of motion whose parameters can be modified while moving are MPIMotionTypeTRAPEZOIDAL, MPIMotionTypeS_CURVE, MPIMotionTypeVELOCITY, MPIMotionTypePT and MPIMotionTypePVT.
Use the MPIMotionAttrAUTO_START attribute to automatically start a motion profile if the MotionModify call is made too late (i.e., after the previous move has finished). It is impossible to use the HOLD attributes with mpiMotionModify, even when using the AUTO_START attribute.
Each axis has a 128 frame buffer (FIFO). mpiMotionStart and mpiMotionModify calls will load up to 10 frames. No provision has been made to check if the new frames will overwrite the currently executing frames. This could happen after about 12 Start/Modify calls are made with the APPEND attribute.
The XMP firmware frame execution time cannot exceed 16,384,000 samples. With the sample rate configured for 2000 (default), the maximum velocity time is 2.27 hours. If the commanded frame exceeds the maximum frame time, the axes will stop abruptly after 16,384,000 samples. The motors will still maintain servo control and no errors are reported.
In trapezoidal or s-curve moves, a frame is a section of motion with constant jerk, constant acceleration, or constant velocity.
In point list motion (PT, PVT, spline, etc), a frame is an individual point in the point list.
For high speed point streaming applications, low-overhead versions of mpiMotionModify and mpiMotionStart are available. See Fast Versions of mpiMotionStart(...) and mpiMotionModify(...).
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