Siemens sinumerik 840D sl Function Manual page 745

Detailed description
2.1 Functional description
Note
Points 3 to 8 can be repeated as often as required.
Following retrace support, a new reverse travel is possible up to a maximum of the last
program continuation point. See Subsection "Detailed description / Functional description /
Retraceable contour area".
Signal chart for interface signals
The principle sequence of the RESU function is illustrated in the following figure "Signal
chart" as a signal chart of the interface signals involved:
10
The first NC START command processes the action blocks. Retrace support ASUB:
CC_RESU_BS_ASUP.SPF is initiated when the last action block is reached:
DB21, ... DBX32.7 = 1
For more about ASUB see Subsection "Detailed description / RESU-specific part
programs".
The second NC START command processes the approach block before part program
processing is resumed.
Special functions: Retrace Support (TE7)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0