<9. Advanced Engineering >
Reference
position
Reference
position
In the figure below, the input to contact C006 in the left LD has been changed.
As the input to contact C006 no longer connects to the left power rail, the line
connecting contact C006 and coil C007 is no longer the reference position. The
new reference position is the line connecting contact C004 and coil C005 as it is
the lowest line connecting the left and right power rails. The reference position of
the left LD is now higher than that of the right LD so the left LD is executed
before the right LD.
Reference
position
Reference
position
To control the execution order for LDs, do not place two or more LD circuits on
the same row. When inserting circuits in the LD editor, place one LD on each
line.
• Reference position for logic combining FBD and LD
Within a code worksheet coded with FBD and LD, the reference position of each
function, function block and NPAS POU changes from its highest point to its
lowest point.
In the figure below, the reference position of the AND logic is changed from its
highest point to its lowest point, which is lower than the reference position of the
LD logic so the AND logic is executed after the LD logic.
Reference
position
Reference
position
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