Interestingly, you can achieve the same functionality without the FP instruction as follows:
Code:
A Start_Pump_Req
AN Start_Pump_Mem
= Start_Pump_Edge
A Start_Pump_Req
= Start_Pump_Mem
This works because the the program is executed sequentially and demonstrates why the memory bit must retain its condition from one one scan to the next. This can be done in ladder too but requires 2 networks. There are ladder equivalents of FP and FN available too.
Nick