I was googling for the proper spec earlier but so far haven't been able to find it :-( (presumably because it's not something hobbyists ever really messed with) -- This has been discussed several times in the past year on cctalk. The best overview was published by National when they were building disc controller chips. Unfortunately, cctalk's archive is out of sync with what Google thinks. Look for "disc simuatlors" as the topic, but look at the cached copy of the page. Here is what I wrote the last time: A good overview of disc formats can be found in two National app notes http://www.national.com/apnotes/Others__v17.html AN-413 AN-501 describes the SMD interface, but National doesn't have it on line any more. It can be found at: http://manuales.elo.utfsm.cl/datasheet/national/pdf/nsc04334.pdf There are lots of other related app notes there related to using their disc chipsets which would be handy as well