AV.link, also known under the trade names nexTViewLink, SmartLink, Q-Link, EasyLink, etc., is a protocol to carry control information between audio-visual devices connected via the

SCART SCART (also known as or , especially in France, 21-pin EuroSCART in marketing by Sharp in Asia, Euroconector in Spain, EuroAV or EXT, or EIA Multiport in the United States, as an EIA interface) is a French-originated standard and associated 2 ...

(EIA Multiport) connector. It is standardised as

CENELEC CENELEC (french: Comité Européen de Normalisation Électrotechnique; en, European Committee for Electrotechnical Standardization) is responsible for European standardization in the area of electrical engineering. Together with ETSI (telecom ...

EN 50157-1. The

Consumer Electronics Control Consumer Electronics Control (CEC) is a feature of HDMI designed to control HDMI connected devices by using only one remote controller; so, individual CEC enabled devices can command and control each other without user intervention, for up to 15 d ...

(CEC) communication channel in

HDMI High-Definition Multimedia Interface (HDMI) is a proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controll ...

and

PDMI PDMI (Portable Digital Media Interface) is an interconnection standard for portable media players. It has been developed by CEA (Consumer Electronics Association) as ANSI/CEA-2017-A standard ''Common Interconnection for Portable Media Players'' ...

is based on AV.link.

Electrical characteristics

AV.Link uses a single wire in an

open collector An open collector is a common type of output found on many integrated circuits (IC), which behaves like a switch that is either connected to ground or disconnected. Instead of outputting a signal of a specific voltage or current, the output sig ...

configuration. It is passively pulled up to 3 or 3.3 V, and may be pulled down by any device on the bus. Total bus capacitance is a maximum of 7300 pF (ten devices at 100 pF each, plus nine cables at 700 pF), and signal transitions are correspondingly slow: 333 bit/s, with 50

μs A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available. A microsecond is equal to 1000 ...

fall time and 250 μs rise time. Each bit transferred begins with a falling edge. The duration of the low period determines the value. Data bits are 2.4±0.35 ms long, with 1 bits having a low period of 0.6±0.2 ms, and 0 bits having a low period of 1.5±0.2 ms. Receivers observe the data line at 1.05±0.2 ms after the falling edge to determine the bit's value. Every message begins with a special start bit, 4.5±0.2 ms long, with a low period of 3.7±0.2 ms. A transmitter must listen to the bus as it transmits; the receiver may hold it low, turning a transmitted 1 bit into a 0 bit. This is done, for example, to acknowledge a transmission. If a receiver detects an error in the received data, it holds the bus low for 3.6±0.24 ms; this causes the transmitter to abort the message and retry from the beginning. A message consists of a start bit, followed by a series of data bytes. Each byte is actually transmitted as 10 bits: * 8 data bits, most significant bit first, * An end-of-message bit is 0 to indicate that more bytes are being transmitted, or 1 to indicate not, and * An acknowledge bit is transmitted as 1, but overwritten to a 0 bit by the receiver to acknowledge receipt. ** For broadcast messages, the acknowledge bit is inverted: it is overwritten to 0 if any receiver ''rejects'' the message. Each message begins with an address byte specifying the 4-bit initiator and recipient addresses. If two initiators begin transmitting at the same time, one of them will transmit a 0 bit while the other transmits a 1 bit, and the latter will observe the conflict and cease transmitting until the bus is idle again. (Note that it must be prepared for the case that the incoming message is addressed to it.) An address byte sent with EOM=1 is a simple "

ping Ping may refer to: Arts and entertainment Fictional characters * Ping, a domesticated Chinese duck in the illustrated book '' The Story about Ping'', first published in 1933 * Ping, a minor character in ''Seinfeld'', an NBC sitcom * Ping, a c ...

" to check if the addressed device exists and is powered on. Otherwise, it is followed by an opcode byte, and parameters as required by the opcode. When a device is powered on, it chooses an address and sends a ping to see if that address is claimed by another device. If no acknowledge is received, the address is free and may be kept. Otherwise, the device tries another address.

References

Designing CEC into your next HDMI Product

HDMI Specification Version 1.3a, Supplement 1: Consumer Electronics Control (CEC)
* {{cite web, url=http://www.npe.sony.co.uk/faq.html , archive-url=https://web.archive.org/web/20031203022152/http://www.npe.sony.co.uk/faq.html , url-status=dead , archive-date=December 3, 2003 , title=Sony Freeview microsite - VTX-D800U FAQ , publisher=

Sony , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...

, quote=Smartlink may be referred to as Megalogic, NexTView, T-V Link, Easylink, AV.Link, CinemaLink, or Q-Link. The VTX-D800U will operate any device which provides the compatible interface. , date=July 6, 2007 , accessdate=January 22, 2010 Audiovisual connectors Film and video technology Television technology

Electrical characteristics

See also

References