Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 539)

Tool Tip Radius Compensation (TTRC)
Function
Chapter 21
21-55
Error detection M-codes are only functional when TTRC is active. TTRC
is active when the control is in G41 or G42 mode and has already made
the entry move into compensation. If an M800 or M801 is programmed
in G40 mode or before the entry move into TTRC takes place, the M code
is ignored.
If error detection is disabled in TTRC, and TTRC is exited (G40
programmed), the next time TTRC is re-activated error detection will be
re-activated automatically. Error detection is always automatically enabled
when cutter compensation is activated.
Refer to documentation prepared by your system installer for the M-codes
used on your specific system.
END OF CHAPTER