According to the standard HDMI CEC bus, it can support up to 15 different devices. In practice, consumer electronics manufacturers realize no more than four by the number of HDMI ports on the TV; support for more, as a rule, is necessary in the industrial sector. This number can support TVs for business and other devices.
When activating HDMI CEC, a new device in the network is registered and receives a logical address; it is selected from free addresses. The device transmits information about itself (TV, player, streaming device, audio device), which is necessary for proper operation. One of the devices is designated as the master; since HDMI is primarily a video interface, a TV or monitor will always be selected as the master.
Understanding HDMI CEC Command Structure
HDMI CEC (Consumer Electronics Control) commands are composed of 10 bits. Typically, these commands are divided into two blocks. The first block identifies the device initiating the command and the target device, while the second block contains the specific command to be executed.
In scenarios where a command does not need to address a particular device, only the command block is transmitted. All devices connected to the CEC bus will receive and execute this command. This is a common occurrence.
For example, consider a setup with a TV, Fire Stick, and soundbar. Regardless of which device is turned on first, the activated device will transmit an HDMI CEC command to power on all devices connected to the CEC bus.
Further, if you are watching a video on a streaming device and wish to pause it, you can use the TV remote control to press the pause button. The TV will generate a pause command and send it to the CEC bus. In this instance, only the Fire Stick will respond to the command since it recognizes the pause function. The soundbar, which does not support this command, will simply ignore it.
