CrossRoads:
Run the RC signal thru a buffer so that it puts out a nice clean edge.
A simple op-amp/comparator would do it - output stays at low level until the cap charges up to the comparison level, and then the output flips, nice & clean.
Logic devices with "schmitt trigger" inputs are designed to do that. Here is an example device
http://www.ti.com/lit/ds/symlink/sn74lvc1g17.pdf
This register has inside trigger with hysteresis, why should I add extra external trigger? 