Open Host Controller Interface, OHCI, is an open standard that allows a computer host to interact with Firewire and USB devices.

When applied to a FireWire card, OHCI means that the card supports a standard interface to the PC and can be used by the OHCI FireWire drivers that come with all modern operating systems. Because the card has a standard OHCI interface, the OS does not need to know in advance exactly who makes the card or how it works, it can safely assume that the card understands the set of well-defined commands that are defined in the standard.

An OHCI standard document from Microsoft and Compaq can be downloaded from ftp://ftp.compaq.com/pub/supportinformation/papers/hcir1_0a.pdf