[P] and POS whats the difference (newbee)

[kolonelvonklink 0]

Hi Can sombody explain me the difference between [P] and POS instructions. I know they are Diff up functions but whats the difference. When should one chose which? If I need to use the diff up of e.g. 126.0 as an input in different rungs, then I need two markers (memory bits), right? like: A I126.0 FP M0.0 = Q0.1 Couldn't this be made more easy, something like AFP I126.0? thanks Edited 4 Oct 2008 by kolonelvonklink

[Mike Dyble 0]

I think it is a matter of personal choice which instruction to use. The Diff up (edge detection) instruction requires a memory bit to remember the state from the previous scan so that the comparision can be made. In your example M0.0 serves as this memory bit. If you want to use the rising edge of I126.0 elsewhere than use Q0.1 going by your example. Hope this helps Mike Edited 7 Oct 2008 by Mike Dyble