"What is M-CODE M97, M98 & M99 (Sub Programs or Sub Routines) Mean in CNC Programming"

M-Code M97, M98 and M99 Subprogramming M-Codes

M97 Local Sub-Program Call (P, L):  

M97 is the M-code Used to call a Subprogram with the reference of the line number N within the same program. Pxxxx code is used as a line number to be repeated. Xxxx is the line number in the same program. This is used for the simple program within the program and does not require complication of creating a sub program. A local sub-program must end with an M99. If there is a repetition of the loop of subprogram L count on the M97 line, the sub-program will be repeated L number of times.

M97 Program Format:

M97 Pxxxx Lnn

Whereas,        xxxx is the line number

                        nn is the number of repetitions

Example:

Main program:

O01234 (Program number and Start of main program)

N0001 T02 M06;

N0002 T03

N0003 G54 G90 G00 Z50

...

...

...  (Part program)

...

M97 P0015 L3 (Jumps to line N0015, after the M30, to execute a local sub-program for 3 times)

...         (The M99 at the end of the sub-program will cause it to jump back here.)

...

...

... (Finish part program)

...

M30 (End of main program)

N0015 (Identifies the start of the Local Sub-Program called up by M97 P0015)

...

... (Local sub-program portion of Main program)

...

M99 (Jumps back to the line after local sub-program call in the main program)

M98 Sub-Program Call (P, L):  

M98 is the M-code Used to call a Subprogram with the reference to the separate program created and loaded on the controller. The Pxxxx code is the sub-program number being called; it must be in the same block as the M98. A sub-program must end with an M99 to enter to main program after the subprogram. If there is a repetition of the loop of subprogram L count on the M98 line, the sub-program will be repeated L number of times before continuing to the next block.

M98 Program Format:

M98 Pxxxx Lnn

Whereas,        xxxx is the line number

                        nn is the number of repetitions

Example:

Main program:

O01234 (Program number and Start of main program)

N0001 T02 M06;

N0002 T03

N0003 G54 G90 G00 Z50

...

...

... (Part program)

...

...

M98 P111 (Jumps to program O00111 to execute sub-program)

... (The M99 at the end of the sub-program will jump back here)

...

... (Finish part program)

...

M30 (End of main program)

Sub-program:

O00111 (Identifies the start of a separate sub-program)

...

... (Sub-program portion of part)

...

M99 (Jumps back to the line after the sub-program call in the main program).

M99 End Sub-Program or Return or Loop:

           This M-code is used to end the sub-program.  If M99 is used in the main program, it will cause the program to loop back to the beginning and repeat over and over again without stopping.

Example:

Main program:

O01234

...

... (Complete part program)

...

...

M99 (This will cause the program to jump back to the beginning and repeat itself)

An M99 without a P code at the end of a sub-program will return to the main Program.)

Main program:

O01234

...

... (Part program)

...

M98 P111 (Jumps to program O00111 to run)

…

... (The M99 at the end of the sub-program will jump back here)

...

... (Finish part)

...

M30 (End of main program)

Sub-program:

O00111 (sub-program number)

...

... (Sub-program portion of part)

...

M99 (Jumps back to the line after the sub-program call)