The $GOTO statement

In addition to the subroutine technique or the use of control block statements ($IF, $FOR...), this functionality offers another option for branching to other program parts. The GOTO command can be called at any point in the NC program by setting jump labels in the NC program.

There are two options to use jump statements:

Expression label:

String label:

Characteristics:

• The $GOTO call can be placed in the NC program before or after the label definition. A label search is carried out in the program in the upwards and downwards directions.
• The label must always be called and defined at the same program level (locally within the program). Program jumps between the main program and a subroutine as well as jumps between subroutines are not permitted (see figure below).
• Identical labels may be defined in main programs and subroutines.
• It is possible to jump to the same label from several points in the NC program.
• A $IF statement may be combined with a $GOTO in the same NC line. In this case, no associated $ELSE/$ENDIF statement may be programmed.
• Other NC commands may be programmed before and after a $GOTO command in the same NC line. However, the jump is the last action in the NC line.
• External jumps are possible to any levels of a $IF-$ELSE-$ENDIF control block and within and between these levels. Then however, this jump-in level is the active level (condition is assumed as true; see Programming example).
• Jumps within $WHILE, $FOR, $DO, $REPEAT are not permitted.
• Complete exit from any control block statement by a $GOTO from any level is always permitted.
• Labels in comments (#COMMENT BEGIN, #COMMENT END) are not recognised.
• In string labels, no distinction is made between uppercase and lowercase.
• All labels ignored during decoding are stored. The maximum number of storable expression labels [6]-6.41, string label [6]-6.42 and string label length [6]-6.43 are specified.
• At each jump call, a check is made whether the jump label already is known, i.e. stored. If the check is positive, the jump is executed immediately. If the jump label is unknown, the search is started in the active program level from the current NC line in the program level through to program end (M29/M30). If the jump label is not found, error message P-ERR-20840 is output.
• After reaching the maximum number of storable labels and other new jump labels are decoded, these labels are no longer saved. This is displayed by the warnings P-ERR-20829 or P-ERR-20831. At every new jump label call with an unknown label, the search starts again at the start of the current program level. In this case, the jump process may require more time with very large NC programs.

Programing Example

The $GOTO statement

%goto

N05  P1=1

N06  P2=1

N10  G74 X1 Y2 Z3

N11      X0 Y0 Z0

N15  $IF P1==1 $GOTO N40: ;   Jump from outside to N40 in a

                          ;   control block

N20  X10

N25  Y10

N30  $IF P1==2

N35    X20

N40:   $IF P2==1

N45    X30

N50:     Y30 $GOTO N65: ;   Jump to N65 between control block levels

                        ;   IF-ELSE

N51    $ENDIF

N55  $ELSE

N60    Y40

N65:   X40

N70  $ENDIF

N80   Z99

N999  M30

Programing Example

N10 G1 XY

N20: X100                              ;Label definition N20:

$IF V.L.dummy_1 <100 $GOTO N20         ;Jump to label N20

$IF V.L.dummy_1 >200

$GOTO [LABEL_1]                        ;Jump to label [LABEL_1]

Y20

$ENDIF

[LABEL_1] X0                           ;Label definition [LABEL_1]

N30 A0

$FOR V.P.my^_var = 0, 4, 1

$IF V.L.dummy_2 <200 $GOTO [CONTINUE]  ;Jump to label [CONTINUE]

$SWITCH V.P.my^_var

$CASE 0

V.P.AXE^_X=V.P.GROUP[1].position[V.P.my^_var]

$BREAK

$CASE 1

V.P.AXE^_Y=V.P.GROUP[1].position[V.P.my^_var]

$BREAK

$CASE 2

V.P.AXE^_Z=V.P.GROUP[1].position[V.P.my^_var]

$BREAK

$CASE 3

V.P.AXE^_A=V.P.GROUP[1].position[V.P.my^_var]

$DEFAULT

$ENDSWITCH

$ENDFOR

[CONTINUE]                       ;Label definition [CONTINUE]

N1000 ...

...