Yeah, it looks like he is wanting greater than 1uSec resolution which just isnt possible. BUT, I do think that he could build a system with opto22 hardware that will accurately determine the winner with resolution close to 50uSec. It is a stretch, but I like opto : )
Take a G4D16R brain. From the datasheet we can infer a typical event/reaction response time for a single point of 250uSec (I would be interested to know if the microcontroller I/O is processed on interrupt or a timer ). Have one rack for each lane with each rack only communicating on interrupt (likely the last photo detector) to reduce brain processor burden. With this setup, any latency in the Opto22 system should be equal and will cancel out. It wouldnt matter if there was a 500uSec delay or 100mSec, as long as both racks repeat-ably experienced the same latency the winner would still be accurately determined. This would of course have to be tested!
To have an event configured as “read and hold counter” the controller absolutely matters. This feature is only available in FactoryFloor and firmwares of that time.
I wouldnt want to build a new system on old hardware though, so…