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3. POSITIONING SIGNALS
[Internal processing]
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(1) On starting the operation, the positioning data of points 0 to 6 ((1) to (14)) is
input to the PCPU.
At this time, the last point of the data to be input - which is point "6" - is stored in
the data set pointer for constant speed control.
The "6" stored in the data set pointer for constant speed control indicates that
updating of the positioning data stored in points 0 to 6 is possible.
(2) The positioning data of points 0 and 1 ((A) to (D)) is updated in accordance with
the sequence program.
The last positioning data to be rewritten - which is the data of point "1" - is
stored in the PC set pointer (which must be controlled by the user in the
sequence program). Updating of positioning data of points 2 to 6 (data (5) to
(14)) remains possible.
(3) On completion of the positioning for point 0, the value in the data set pointer for
constant speed control is automatically incremented by one to "7".
At this time, the positioning data of point 0 ((1) to (2)) is discarded and the
positioning data for point 7 ((15) to (16)) is input to the PCPU.
(4) Hereafter, each time the positioning for a point is completed, the positioning
data shifts one place.
The positioning data that can be updated is the data after that indicated by the
PC set pointer: this is the data which has not yet been input to the PCPU.
Consequently, after completion of the positioning corresponding to point 3,
even if the values stored in indirect devices D8 and D10 are updated by the
sequence program, the point 2 positioning data that is input to the PCPU will
not be updated and the second positioning will be executed using the
unupdated data.
In other words, the data set pointer for constant speed control is a pointer that
indicates data that has not yet been input to the PCPU and can be updated by
the sequence program.
POINT
Number of points that can be defined by a repeat instruction
• Create a subprogram to create at least eight points.
• If there are less than eight points and these include pass points with small
travel values, the positioning at each point may be completed, and the data
input to the PCPU, before the data has been updated by the sequence
program.
• Create a sufficient number of points to ensure that data will not be input to
the PCPU before the SCPU has updated the values in the indirect devices.
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