Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 733)

Program Interrupts and
Dressing Interrupts
Chapter 22
22-13
Number of retrace blocks for dressing interrupts
You can alter the number of blocks that the control retraces when returning
to the start position of the interrupt. The default number of retraced blocks is
4. Alter the number of retrace blocks by programming one of these M codes:
Programming an: retraces:
M900 zero blocks
M901 one block
M902 two blocks
M903 three blocks
M904 four blocks
You can program these M codes in any block in the calling program before
the control executes the dressing interrupt program. You can also program
them within an interrupt, though the M code does not go into effect until
execution is returned to the calling program. If not programmed, the
default is four blocks. The default is automatically reset at the
end-of-program commands (M02 or M30), E-STOP reset, or control reset.
The number of retrace blocks as set with this M code is the same for all
active or inactive interrupts. If an interrupt is enabled after this M code is
programmed, it takes on the number of retrace blocks as programmed with
this M code.
When the return from interrupt is executed (M99 in the interrupt), the
control generates a linear move to the end-point of the last-remembered
move for retrace. The moves are then retraced, returning the tool back to
the start-point of the interrupt. This may not be the same location in the
main program if a different tool offset has been activated.
Remember when you use a program as an interrupt program for both types
of interrupts (program interrupts as well as dressing interrupts):
Any modal data (G codes, feedrates, spindle speeds, coordinate system
offsets, etc.) contained in the calling program are carried into the
interrupt program. Any changes made to this modal data within the
interrupt are effective only in the interrupt program; changes are not
carried back into the calling program when the interrupt is completed.
This does not include wheel or wheel offset data that is changed in the
interrupt. Any wheel or wheel offset changes are carried back into the
suspended calling part program.
22.3
The Interrupt Program (P
word)