A USB and Firewire Host Controller Interface (UFHC) is a register-level

interface Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * '' Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Inter ...

that enables a

host controller In computer hardware a host controller, host adapter or host bus adapter (HBA) connects a computer system bus which acts as the host system to other computer network, network and computer storage, storage devices. The terms are primarily used ...

for

USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

IEEE 1394 IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony a ...

hardware to communicate with a host controller driver in software. The driver software is typically provided with an

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

of a

personal computer A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...

, but may also be implemented by application-specific devices such as a

microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...

. On the

expansion card In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus sl ...

or motherboard controller, this involves much custom logic, with digital logic engines in the motherboard's controller chip, plus analog circuitry managing the high-speed differential signals. On the

software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

side, it requires a

device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...

(called a Host Controller Driver, or HCD).

IEEE 1394

Open Host Controller Interface

Open Host Controller Interface (OHCI) is an

open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a common prerequisite that open standards use an open license that provides for extensibility. Typically, anybody can participate in their development due to ...

. When applied to an

(also known as

FireWire IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony a ...

; i.LINK or Lynx) card, OHCI means that the card supports a standard interface to the PC and can be used by the OHCI IEEE 1394 drivers that come with all modern

s. 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 protocol.

USB

Open Host Controller Interface

The OHCI standard for

is similar to the OHCI standard for IEEE 1394, but supports USB 1.1 (full and low speeds) only; so as a result its register interface looks completely different. Compared with UHCI, it moves more intelligence into the controller, and thus is accordingly much more efficient; this was part of the motivation for defining it. If a computer provides non-x86 USB 1.1, or x86 USB 1.1 from a USB controller that is not made by Intel or VIA, it probably uses OHCI (e.g. OHCI is common on add-in PCI Cards based on an NEC chipset). It has many fewer intellectual property restrictions than UHCI. It only supports 32-bit memory addressing, so it requires an IOMMU or a computationally expensive bounce buffer to work with a 64-bit operating system. OHCI interfaces to the rest of the computer only with

memory-mapped I/O Memory-mapped I/O (MMIO) and port-mapped I/O (PMIO) are two complementary methods of performing input/output (I/O) between the central processing unit (CPU) and peripheral devices in a computer (often mediating access via chipset). An altern ...

Universal Host Controller Interface

Universal Host Controller Interface (UHCI) is a

proprietary {{Short pages monitor