High-definition multimedia interface-consumer electronics control (HDMI-CEC)
1 High-definition multimedia interface-consumer electronics control (HDMI-CEC)
AN4066
1.1 Introduction
Consumer electronics control (CEC) is the appendix supplement 1 to the HDMI (high definition multimedia interface) standard.
It is a protocol which provides high-level control functions between all of the various audiovisual products in an environment. It is specified to operate at low speeds with minimum processing and memory overhead.
For more details, refer to the high-definition multimedia interface specification
(www.hdmi.org).
The CEC bus is a single-wire protocol which can connect up to 10 audiovisual devices through standard HDMI cabling.
All transactions on the CEC line consist of an initiator and one or more followers. The initiator is responsible for sending the message structure and the data. The follower is the recipient of any data and is responsible for setting any acknowledgement bits.
A message is conveyed in a single frame which consists of a start bit followed by a header block and, optionally, an opcode and a variable number of operand blocks.
Figure 1.
shows
a CEC frame format.
Figure 1.
CEC frame format
6/32
Figure 2.
Message structure
high Start impedance Bit
Header Opcode Operand
0 to 14 operands
Operand high impedance
Doc ID 022911 Rev 1
