Siemens sinumerik 840D sl Function Manual page 258

Detailed description
2.2 Curve tables
Note
The value pairs between CTABDEF and CTABEND must be specified for precisely the axis
identifiers that have been programmed in CTABDEF as the leading axis and following axis
identifiers. In the case of programming errors, alarms or incorrect contours may be
generated.
2.2.5 Access to table positions and table segments
Reading table positions
With the program commands CTAB and CTABINV the following value for a master value
(CTAB) can be read from the parts program and from synchronous actions, or alternatively
the master value can be read off for a following value. The pitch value can be used to
calculate the speed of the following axis or leading axis at any position in the table.
Reading segment positions
Segment positions of a curve table for the value for the following axis can be read using the
CTABSSV and CTABSEV calls.
The language commands CTABSSV and CTABSEV generally provide the start and end values
of the internal segments of the curve tables for the following axis. These values only agree
with the programmed values of the curve tables if the programmed segments can be
converted 1:1 to the internal segments of the curve table. This is always the case if only G1
blocks or axis polynomials are used to define the curve tables and no other functions are
active.
Programmed sections may under certain circumstances not be transformed unchanged into
internal curve segements if:
1. Circles or involutes are programmed
2. Chamfer or rounding is active (CHF, RND)
3. Smoothing with G643 is active
4. Compressor is active (COMPON, COMPCURV, COMPCAD)
5. Tool radius compensation is active for polynomial interpolation.
In these cases, the language commands CTABSSV and CTABSEV may not be used to query
the start and end points of the programmed segments.
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Special functions: Axis Couplings and ESR (M3)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0