Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 739)

Program Interrupt
Chapter 29
29-9
The system installer determines if an interrupt program is to be called as
a paramacro or a subprogram when it executes.
If it is Called: Then:
A Paramacro This assigns a new set of local parameters for the
interrupt
A Subprogram The same set of local parameters that applied to the
interrupted program apply to the subprogram.
If an interrupt is chosen as a macro program, it may not be a macro that
requires the assignment of local variables in the calling block (cannot
require an argument).
Macro type interrupts are always called as the G65 non-modal type.
G66 and G66.1 modal types may not be called. Refer to the chapter on
paramacros for details on the G65 type macros.
The interrupt program must contain an M99 block. Any axis motion
commands that are to the left of the M99 code in the block will result as
an error. Other programming commands to the left of the M99 code in
the block will be executed. Any characters to the right of the M99 code
in the block are ignored.
If using a type 2 interrupt (L1, L2, or L3), remember that the control
remembers as many as the first 4 blocks in the program and uses these
to retrace its moves back to the starting point of the interrupt program.
The control remembers as many as 4 of the first moves or until a
circular block is executed. For details, see section 29.3 on interrupt
types.
The interrupt program may contain a milling cycle in the interrupt.
Coordinate system offsets are illegal in an interrupt program. This
includes G52, G92, G92.1, and G92.2.
Any inherent modality from the main program (such as a milling cycle,
or an active modal paramacro) will be temporarily canceled during the
execution of a interrupt program.
Although all four interrupts can be active at once, only one interrupt can
be executing at any given time.
END OF CHAPTER