hmmm interesting, i had been wanting to capture a DMX512 (based on RS485) frame and decode for fun (iirc variable number of packets up to 512). if so, would it be better off to get a dedicated datacapture probe? (one of those USB types maybe? instead of using rigols?)
For protocol analysis, a device that is designed as a protocol analyzer first will nearly always outperform a device designed as an oscilloscope first.