We offer two Universal Motor Interfaces that allow encoder frequencies of 1 MHz or 20MHz. the UMI with 1MHz capabilites has an additional low pass filter applied to the incoming signal.The following includes links to the 7764, and an additional link to a KB that may be useful.
http://sine.ni.com/apps/we/nioc.vp?cid=3970〈=US
http://digital.ni.com/public.nsf/websearch/0A89C125C732520E862567FB00701A52?OpenDocument
I hope this helps!
Chris D
