Counting chain links on a conveyor

[yomp]

Bit of a begineer here (first post), I have been asked to look at conveyor chain links on a conveyor that carry fixed magnetic grids to hold metal pans. These grids can get damaged and we want to inspect each grid. At the moment I am programming using GXworks to a FX2N and then using a Proface HMI to show data and have some simple counting logic to count up the chain links (3785 of them). So from 1 to 3785 the plan is to count up and show the count on the HMI and go back to 1 after I reach 3875 chain links as the conveyor does one full revolution. However, sometimes after a crash the chain has to be reversed. If it is reveresed at chain link (for example) No.2 the counter goes 2,1,0,-1,-2,-3 , etc etc, when I need the count to read 2,1,3785,3784,3783 etc etc. 

How best to tackle this problem?

Thanks

Graham

[yomp]

Solved it but it looks ugly! See file. Maybe look at it again once everything else is ready. I need to change the "10" values to the actual number of grids.

grid counter.pdf

Edited March 29, 2020 by yomp

[WattUp]

---| Running Reverse | --- [ = Count K1 ] ---------------- [ MOV K3785 Count ]