HEIDENHAIN TNC 320 User Manual page 72

Please note while programming:
Program a positioning block for the starting point (hole
center) in the working plane with radius compensation R0.
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program
DEPTH=0, the cycle will not be executed.
Danger of collision!
Use the machine parameter displayDepthErr to define
whether, if a positive depth is entered, the TNC should
output an error message (on) or not (off).
Keep in mind that the TNC reverses the calculation for pre-
positioning when a positive depth is entered. This
means that the tool moves at rapid traverse in the tool axis
to set-up clearance below the workpiece surface!
72 Fixed Cycles: Drilling