HEIDENHAIN TNC 306 Technical Manual - Manual (Page 400)

7-110
TNC 416/TNC 406/TNC 306 Commands 3/2000
3.17.2 REPEAT ... UNTIL Structure
The REPEAT ... UNTIL structure repeats a program sequence until a condition is fulfilled.
Under no circumstances may this structure wait for an external event in the cyclical PLC
program to happen!
The following commands are available:
•
REPEAT (Repeat) Repeat program sequence from here
•
UNTILT (Until True) Repeat sequence until Logic Accumulator=1
•
UNTILF (Until False) Repeat sequence until Logic Accumulator=0
A REPEAT ... UNTIL loop is always run at least once!
Example:
= M100 ;end of previous chain
REPEAT ;repeat following code
..... ;code to be executed
LX ;load Index Register
>= K100 ;check Index Register
UNTILT ;repeat until X>=100
3.17.3 WHILE ... ENDW Structure
The WHILE ... ENDW structure repeats a program sequence if a condition is fulfilled.
Under no circumstances must this structure wait for an external event in the cyclical PLC program to
happen!
The following commands are available:
•
WHILET (While True) Execute sequence if Logic Accumulator=1
•
WHILEF (While False) Execute sequence if Logic Accumulator=0
•
ENDW (End While) End of program sequence, go back to beginning
A WHILE ... ENDW loop is only run when the WHILE condition is fulfilled at the beginning. The
execution condition must be repeated before the ENDW instruction. The condition can also be
repeated differently than before the WHILE instruction!
Example:
.....
L
M100 ;create condition for 1st WHILE scan
WHILET ;execute following code if Logic Accumulator = 1
..... ;code to be executed
L M101 ;create condition for repeat processing
A M102 ;next condition
ENDW ;return to WHILE scan
Two internal jump labels are generated for the WHILE ... ENDW structure.