Mitsubishi Electric MELSEC Q Series Programming Manual page 103

3 POSITIONING DEDICATED SIGNALS
[Internal processing]
(a) The positioning data ((1) to (16)) of points 0 to 7 is input to the Motion CPU
by the constant-speed control starting process (before positioning start). The
last point "7" of the input data to be input is stored in the data set pointer for
constant-speed control at this time. Because the positioning for point 0 starts
immediately after, space opens in the input area for positioning data and the
Motion CPU inputs point 8 ((17) to (18)) positioning data. The last point "8"
of the input data is stored in the data set pointer for constant-speed control.
The "8" stored in the data set pointer for constant-speed control indicates
that the second updating of the positioning data stored in points 0 to 8 is
possible.
(b) The positioning data ((1) to (4)) of points 0 to 1 is updated to positioning data
((A) to (D)) using the Motion SFC program.
The last point "1" of the updated positioning data is stored in the updated
data set pointer (the user must create a Motion SFC program) at this time.
Positioning data of points 2 to 8 (data (5) to (18)) can still be updated.
However, the positioning data ((A) to (D)) of the updated points 0 to 1 can
also be updated because at this point it has still not been input to the Motion
CPU.
(c) On completion of the positioning for point 0, point 1 positioning starts, the
Motion CPU discards the positioning data ((3) to (4)) of point 1, and inputs
the positioning data ((A) to (B)) of point 0 (second positioning).
At this time, the value of the data set pointer for constant-speed control
automatically proceeds and changes to "0".
(d) Hereafter, whenever positioning of each point is completed, the positioning
data shifts one place.
The positioning data that can be updated is the data which has not yet been
input to the Motion CPU.
Even if the values of the indirect devices D3008 and D3010 are updated by
the Motion SFC program after the positioning completion of the point 3, the
positioning data of point 2 that is input to the Motion CPU will not be updated
and the second positioning will be executed using the unupdated data. The
data set pointer for constant-speed control has not yet been input to the
Motion CPU, and indicates the positioning data which a user can update
using the Motion SFC program.
POINT
Number of points that can be defined by a repeat instruction
• The Motion CPU inputs 8 points in advance, so create a servo program of at least
9 points.
• Even when there are 9 points or more, if pass points with small travel values are
included the positioning at each point may complete, and the data input to the
Motion CPU, before the data has been updated using the Motion SFC program.
• Create a sufficient number of points to ensure that data will not be input before the
Motion CPU has updated the values in the indirect devices.
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