692 HEIDENHAIN Technical Manual MANUALplus 620
6.9 PLC Axes
Axes that are not in an interpolation context can be used by the PLC as
required. The PLC can start more than one axis simultaneously, but they are
not interpolated with each other. As soon as an axis is not part of the active
kinematics, you can use the axis as PLC axis.
Stopping/Starting
axes by PLC
Module 9120 Position PLC axis
Module 9120 positions PLC axes that are assigned to the PLC. By entering a
target position (in the reference system), a feed rate and a flag register, the
positioning of a PLC axis is started. The axis is positioned regardless of any
other processes in the control. In particular, there is no path interpolation with
other axes.
Constraints:
The axis must not be in an interpolation context.
The parameter values for rapid traverse, acceleration, etc. must be set
correctly.
Rotary axes are positioned in the direction of the shortest path, except if the
target position was transferred as an incremental value.
Software limit switches are not active.
The axis must be stationary. Any positioning movement must be aborted
beforehand with Module 9121.
Feed-rate override is disabled.
If no reference mark has been traversed, the positioning process builds on
the counter value as it was upon switch-on.
If Modules 9120, 9121 and 9122 are called more than once for the same axis
during one PLC scan, only the last command is transferred.
A "positioning error" status set in this axis is cleared. The status must be
evaluated by Module 9122.
An axis that is not configured as "active", or an axis that was set to the
"deactivated axis" activation status (e.g. with Module 9226 or 9418), is
treated as if it were not present.
Possible errors:
A non-existing axis was transferred.
An axis was transferred that was not declared as an auxiliary axis with MP10
and MP60 (MPs are only valid for non-symbolic memory interfaces).
For a modulo axis, an absolute target position was transferred that is outside
the permissible interval (0..modulo value).
The axis is already being positioned.
An axis currently not in a closed loop was programmed.
An invalid feed rate was programmed.
Please keep in mind that the axis interpolation context can be changed
dynamically, for example by the activation of another kinematic model.
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