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USER MANUAL Chapter 6 Programming Motion • 69
It is the responsibility of the user to keep enough LI segments in the DMC-13X8 sequence buffer to
ensure continuous motion. If the controller receives no additional LI segments and no LE command,
the controller will stop motion instantly at the last vector. There will be no controlled deceleration.
LM? or _LM returns the available spaces for LI segments that can be sent to the buffer. 511 returned
means the buffer is empty and 511 LI segments can be sent. A zero means the buffer is full and no
additional segments can be sent. As long as the buffer is not full, additional LI segments can be sent at
PC bus speeds.
The instruction _CS returns the segment counter. As the segments are processed, _CS increases,
starting at zero. This function allows the host computer to determine which segment is being
processed.
Additional Commands
The commands VS n, VA n, and VD n are used to specify the vector speed, acceleration and
deceleration. The DMC-13X8 computes the vector speed based on the axes specified in the LM mode.
For example, LM XYZ designates linear interpolation for the X,Y and Z axes. The vector speed for
this example would be computed using the equation:
VS
2
=XS
2
+YS
2
+ZS
2
, where XS, YS and ZS are the speed of the X,Y and Z axes.
The controller always uses the axis specifications from LM, not LI, to compute the speed.
VT is used to set the S-curve smoothing constant for coordinated moves. The command AV n is the
‘After Vector’ trippoint, which halts program execution until the vector distance of n has been reached.
An Example of Linear Interpolation Motion:
#LMOVE label
DP 0,0 Define position of X and Y axes to be 0
LMXY Define linear mode between X and Y axes.
LI 5000,0 Specify first linear segment
LI 0,5000 Specify second linear segment
LE End linear segments
VS 4000 Specify vector speed
BGS Begin motion sequence
AV 4000 Set trippoint to wait until vector distance of 4000 is reached
VS 1000 Change vector speed
AV 5000 Set trippoint to wait until vector distance of 5000 is reached
VS 4000 Change vector speed
EN Program end
In this example, the XY system is required to perform a 90° turn. In order to slow the speed around
the corner, we use the AV 4000 trippoint, which slows the speed to 1000 count/s. Once the motors
reach the corner, the speed is increased back to 4000 cts / s.
Specifying Vector Speed for Each Segment
The instruction VS has an immediate effect and, therefore, must be given at the required time. In some
applications, such as CNC, it is necessary to attach various speeds to different motion segments. This
can be done by two functions: < n and > m
For example: LI x,y,z,w < n >m
The first command, < n, is equivalent to commanding VSn at the start of the given segment and will
cause an acceleration toward the new commanded speeds, subjects to the other constraints.