Negative transition in Directsoft 440

Dear all,

I want to use a negative transition input signal. I use the PD for my single scan signals for lo to hi transitions. Now I am looking for hi to lo transition. I saw an instruction called STRNB from direct soft help and that would have been perfect but unfortunately this instruction is not available for dl440 which is the cpu I use. My question is is there a clean way to build a hi to low transition? I tried use latch , set. rst but not too clean. Can i use PD somehow backwards as a ND.

Thanks

I do not know about available instructions in Directsoft 440 but a simple way to construct a one shot falling or negative transition input signal from a positive transition is to use NC of the input in front of the positive transition instruction.

STRN C0
ANDSTRN SP0
ANDSTR xxx - Permissives go here to lock out accidental firing.
PD C0