CEC HDMI Conference Final

2008

Developers ConferenceTaipei, Taiwan

An Introduction to Consumer Electronics Control (CEC)

Quantum Data, Inc.

What is CEC? – Quick Facts

CEC stands for Consumer Electronics Control. It’s a one-wire bus (pin 13) that “snakes”

through an HDMI system - allowing products to pass messages to one another.

CEC runs at approx. 400Hz, so including flow control bits and idle timing requirements on the line, it can send approximately 30 bytes each second.

Commands need to be very efficient.

CEC: A Bit of History

In Europe, there was an analog predecessor to HDMI known as the SCART interface.

Like HDMI, SCART carried audio and video signals through one cable.

The SCART cable had a one-wire bus for controlling a home theater system. This was branded as AV.link by Philips, among others.

This bus supported one touch play, standby, etc.

How To Find CEC Devices

CEC is available in many HDMI products today! Limited multi-vendor interoperability.

Manufacturer Name

Panasonic EZSync / HDAVI Control (USA), Viera Link (Japan)

Sony Bravia Theater Sync (USA), Bravia Link (Japan)

Sharp AQUOS FamiLink

Toshiba CE-Link (USA), Regza Link (Japan)

Samsung AnyNet+

LG SimpLink

What is the benefit of CEC?

Today’s HDMI systems are comprised of separate components (digital set top boxes, audio receivers/amps, a DVD player, etc.), which are not always easy to configure & operate.

The general public has difficulty with the how/when/why to set up these devices in order to use them. The more devices, the more complex is the setup.

CEC is a solution to this problem! CEC uses signal routing to allow devices to be

configured across a system - rather than just point-to-point. Examples are one touch play and one touch record which greatly simplify the user experience.

CEC Messaging

CEC Messaging – Quick Facts

CEC messages generally consist of two functional categories:– Request – asking another device(s) to take action or to give

information (e.g. asking a device to play, go into standby, switch sources, or request a device’s physical address).

– Informative – status messages and messages describing where a devices is in a network (e.g. report physical address, report vendor ID).

CEC messages can also be grouped in terms of the intended target device:

– Directed Message - sent to a single CEC device.– Broadcast - sent to all devices in the CEC network.

CEC messages can be up to 16 blocks total (including the header and opcode blocks). If they were longer, they would impede access to the CEC bus due to the speed of the bus. (Sending 16 blocks successfully takes about 0.4s).

The shortest message that can be sent is the polling message, which is simply a start bit followed by a header block.

Devices must respond to a message in 1 second or less, but the desired response time is 200 msec.

CEC Messaging – Blocks and Frames

CEC Data BlockCEC Data Block

Information Bits End ofMessage

Acknowledgment

CEC Header BlockCEC Header Block

Logical Address ofInitiator

Logical Address of

Destination

End ofMessage

Acknowledgment

A CEC message block includes the 8 data bits as well as two extra bits:

End of message – set to 0 for every block except the final block of the message where it

is set to 1.

Acknowledgement (ACK) – set to 1 for every block.

CEC FrameCEC Frame

Start Bit

HeaderBlock

Optional DataBlocks

Image View On – 40 04

Routing Change - 5F 80 13 00

Example Messages:

CEC at Work

CEC at Work – One Touch Play

Image View On (40 04)

DVD DTV

DTV

AVR

DVD Game System STB-DVR

01 00:00:11.01 00:00:00.00 PLAYER1->TV CEC CEC IMAGE VIEW ON01 00:00:11.01 00:00:00.00 PLAYER1->TV CEC CEC IMAGE VIEW ON

02 00:00:11.07 00:00:00.60 PLAYER1->ALL CEC CEC ACTIVE SOURCE02 00:00:11.07 00:00:00.60 PLAYER1->ALL CEC CEC ACTIVE SOURCE

03 00:00:12.21 00:00:01.60 AUDIO->ALL CEC CEC REQUEST ACTIVE SRC03 00:00:12.21 00:00:01.60 AUDIO->ALL CEC CEC REQUEST ACTIVE SRC

04 00:00:18.41 00:00:06.20 PLAYER1->ALL CEC CEC ACTIVE SOURCE04 00:00:18.41 00:00:06.20 PLAYER1->ALL CEC CEC ACTIVE SOURCEActive Source (4F 82 11 00)

DVD ALL

Request Active Source(5F 85)

Request Active Source (5F 85)

DVD DTVAVR

Active Source (4F 82 11 00)

DVD ALL

Request Active Source (0F 85)

ALLDTV


DVD ALL

05 00:00:12.21 00:00:01.60 TV->ALL CEC CEC REQUEST ACTIVE SRC05 00:00:12.21 00:00:01.60 TV->ALL CEC CEC REQUEST ACTIVE SRC


Device functions, actions, message simulation only, 3 ports AVR

CEC at Work – One Touch Play

DTV

AVR


01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC IMAGE VIEW ON01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC IMAGE VIEW ON

02 00:00:11.07 00:00:00.60 TV->TUNER CEC CEC SET STREAM PATH02 00:00:11.07 00:00:00.60 TV->TUNER CEC CEC SET STREAM PATH

03 00:00:12.21 00:00:01.60 TUNER->ALL CEC CEC ACTIVE SOURCE03 00:00:12.21 00:00:01.60 TUNER->ALL CEC CEC ACTIVE SOURCE



STB-DVR DTV

STB-DVR ALL

Set Stream Path (03 86 13 00)

Ch. 2Ch. 3Ch. 4

DTV Remote

CEC at Work – Device Menu Control

DTV

AVR


Menu Status (Activate) (30 8E 00)

User Control Released (03 45 XX)

User Control Pressed (03 44 XX)

STB-DVR DTV

Menu Request (Activate) (03 8D 00)

Menu Request (Deactivate) (03 8D 01)

Menu Status (Deactivate) (30 8E 01)

Ch. 2Ch. 3Ch. 4


STB-DVR DTV


STB-DVR ALL



DTVRemote

03 00:00:11.01 00:00:00.00 TV->TUNER CEC CEC MENU REQUEST03 00:00:11.01 00:00:00.00 TV->TUNER CEC CEC MENU REQUEST

04 00:00:11.07 00:00:00.60 TUNER->TV CEC CEC MENU STATUS04 00:00:11.07 00:00:00.60 TUNER->TV CEC CEC MENU STATUS

05 00:00:12.21 00:00:01.60 TV->TUNER CEC CEC USER CNTL PRESSED05 00:00:12.21 00:00:01.60 TV->TUNER CEC CEC USER CNTL PRESSED

06 00:00:18.41 00:00:06.20 TV->TUNER CEC CEC USER CNTL RELEASED06 00:00:18.41 00:00:06.20 TV->TUNER CEC CEC USER CNTL RELEASED

07 00:00:19.00 00:00:00.59 TUNER->TV CEC CEC MENU REQUEST07 00:00:19.00 00:00:00.59 TUNER->TV CEC CEC MENU REQUEST

08 00:00:19.59 00:00:00.50 TV->TUNER CEC CEC MENU STATUS08 00:00:19.59 00:00:00.50 TV->TUNER CEC CEC MENU STATUS

CEC at Work: One Touch Record

AVR


DTV STB-DVR

Record TV Screen (10 0F)

Record Status [Recording Digital Service] (10 0A 02)

Record ON [Digital Service ID] (01 09 02)

01 00:00:18.41 00:00:00.00 RECORDER->TV CEC CEC RECORD TV SCREEN01 00:00:18.41 00:00:00.00 RECORDER->TV CEC CEC RECORD TV SCREEN

02 00:00:69.51 00:00:51.10 TV->RECORDER CEC CEC RECORD ON02 00:00:69.51 00:00:51.10 TV->RECORDER CEC CEC RECORD ON

03 00:00:69.71 00:00:00.20 RECORDER->TV CEC CEC RECORD STATUS03 00:00:69.71 00:00:00.20 RECORDER->TV CEC CEC RECORD STATUS

DTV

CEC at Work – Deck Control

DTV

AVR


01 00:00:11.01 00:00:00.00 TV->PLAYER CEC CEC PLAY FORWARD01 00:00:11.01 00:00:00.00 TV->PLAYER CEC CEC PLAY FORWARD

02 00:00:11.07 00:00:00.60 PLAYER->TV CEC CEC PLAY STATUS02 00:00:11.07 00:00:00.60 PLAYER->TV CEC CEC PLAY STATUS

Play [Forward] (04 41 24)

DTV DVD

Deck Status [Play] (40 1B 11)

DTV Remote

Deck Control [Skip Forward] (04 42 01)

Deck Status [Skip Forward] (40 1B 17)

03 00:00:11.01 00:00:00.00 TV->PLAYER CEC CEC SKIP FORWARD03 00:00:11.01 00:00:00.00 TV->PLAYER CEC CEC SKIP FORWARD

04 00:00:11.07 00:00:00.60 PLAYER->TV CEC CEC SKIP STATUS04 00:00:11.07 00:00:00.60 PLAYER->TV CEC CEC SKIP STATUS

CEC at Work - Shutdown

DTV

AVR


01 00:00:11.01 00:00:00.00 TV->*ALL* CEC CEC STANDBY01 00:00:11.01 00:00:00.00 TV->*ALL* CEC CEC STANDBY

Standby (0F 36)

DTV ALL

CEC Addressing

CEC Addressing

CEC assumes that all AV source products in a system are directly or indirectly connected to a “root” display (DTV).

HDMI connections form an upside-down tree, with a display as the “root”, switches as “branches”, and various source products as “leaf” nodes.

There are two types of addressing:– Logical– Physical

Logical Addressing

Logical addressing is what CEC uses to identify a specific instance of a specific device type. When messages are sent over CEC, the logical address identifies both the sender (“Initiator”) and intended receiver (“Follower”) of the message.

Logical addressing is done with nybbles (4-bit numbers, allowing for addresses from 0-15). Because of this, the header blocks are simply in “to, from” format – the first four bits sent are the address of the initiator (or sender), while the latter four bits are the follower’s (receiver’s) address.

CEC Header BlockCEC Header BlockLogical Address of

InitiatorLogical Address of

FollowerEnd of

MessageAcknowledgment

Logical Addressing (continued)

Logical addresses are split among device types:– 0 is a TV– 1,2 & 9 are recorders (HDD, DVD, BD, etc.)– 3,6,7 & 10 are tuner devices (i.e. set-top boxes)– 4,8 & 11 are players (DVD, VCR, Blu-Ray, etc.)– 5 is an audio system– 12 & 13 are reserved– 14 is a wild-card– 15 means “Unregistered” if it’s the initiator address,

“Broadcast” if it’s the follower address.

Physical Addressing

Physical addressing describes the topology, i.e. what devices are between the CEC device and the TV, and through what inputs it is connected.

Physical addressing is a required feature for ALL HDMI devices (regardless of whether or not they support CEC), and is essential for routing control, among other things.

Physical Addressing Description

A TV (that does not have HDMI outputs) will use physical address [0.0.0.0]. Any device with an HDMI output will have an address that contains at least one non-zero number, which is grabbed from the HDMI vendor specific data block (VSDB) of the sink device’s EDID.

Devices with both a source and a sink must read the physical address from the EDID of the sink device that it is attached to, and configure its own EDIDs on its sink ports so that they contain the proper physical addresses.

CEC Addressing – Physical Addressing

DTV

AVR


PA 1100PA 1100 PA 1200PA 1200 PA 1300PA 1300

PA 1000PA 1000

PA 0000PA 0000

1100 1200

1000

1300

Physical Addressing – VSDB of EDID

1100

CEC Addressing – Logical Addressing


LA 04LA 04

LA 05LA 05

LA 0PA 0000

LA 0PA 0000

LA 1100LA 04LA 08

PA 1000

Polling Message (F5)

Unregistered AVR

Report Physical Address (0F 84 00 00)



Unregistered DVD



Unregistered Game System


01 00:00:10:0174 00:00:01:0100 TV->*ALL* CEC CEC REPORT PHYSICAL ADDRESS01 00:00:10:0174 00:00:01:0100 TV->*ALL* CEC CEC REPORT PHYSICAL ADDRESS

02 00:00:11.0274 00:00:00:0060 UNREG->AUDIO CEC CEC CEC PING - NACK02 00:00:11.0274 00:00:00:0060 UNREG->AUDIO CEC CEC CEC PING - NACK

03 00:00:11:0639 00:00:00:1000 AUDIO->*ALL* CEC CEC REPORT PHYSICAL ADDRESS03 00:00:11:0639 00:00:00:1000 AUDIO->*ALL* CEC CEC REPORT PHYSICAL ADDRESS

04 00:00:11:1639 00:00:00:0100 UNREG->PLAYER1 CEC CEC CEC PING - NACK04 00:00:11:1639 00:00:00:0100 UNREG->PLAYER1 CEC CEC CEC PING - NACK

05 00:00:11:1739 00:00:00:0251 PLAYER1->*ALL* CEC CEC REPORT PHYSICAL ADDRESS05 00:00:11:1739 00:00:00:0251 PLAYER1->*ALL* CEC CEC REPORT PHYSICAL ADDRESS

06 00:00:11:1990 00:00:00:0028 UNREG->PLAYER1 CEC CEC CEC PING06 00:00:11:1990 00:00:00:0028 UNREG->PLAYER1 CEC CEC CEC PING

AVR


AcknowledgedPA 1200


08 00:00:11:2140 00:00:00:0100 PLAYER2->*ALL* CEC CEC REPORT PHYSICAL ADDRESS08 00:00:11:2140 00:00:00:0100 PLAYER2->*ALL* CEC CEC REPORT PHYSICAL ADDRESS

AVR ALL

DVD ALL

Game System ALL

DTV ALL

DTV

01 00:00:10:0174 00:00:01:0100 TV->ALL CEC CEC REPORT PHYSICAL ADDRESS01 00:00:10:0174 00:00:01:0100 TV->ALL CEC CEC REPORT PHYSICAL ADDRESS

02 00:00:11.0274 00:00:00:0060 UNREG->AUDIO CEC CEC CEC PING - NACK02 00:00:11.0274 00:00:00:0060 UNREG->AUDIO CEC CEC CEC PING - NACK

03 00:00:11:0639 00:00:00:1000 AUDIO->ALL CEC CEC REPORT PHYSICAL ADDRESS03 00:00:11:0639 00:00:00:1000 AUDIO->ALL CEC CEC REPORT PHYSICAL ADDRESS


05 00:00:11:1739 00:00:00:0251 PLAYER1->ALL CEC CEC REPORT PHYSICAL ADDRESS05 00:00:11:1739 00:00:00:0251 PLAYER1->ALL CEC CEC REPORT PHYSICAL ADDRESS

06 00:00:11:1990 00:00:00:0028 UNREG->PLAYER1 CEC CEC CEC PING06 00:00:11:1990 00:00:00:0028 UNREG->PLAYER1 CEC CEC CEC PING






LA 03LA 01


DTV

AVR

Unregistered STB-DVR

Unregistered STB-DVR

LA 04LA 04

LA 05LA 05

LA 0PA 0000

LA 0PA 0000

LA 1100

LA 08PA 1000

PA 1200PA 1300

DTV

CEC Addressing – Logical Addressing

08 00:00:11:2140 00:00:00:0100 PLAYER2->ALL CEC CEC REPORT PHYSICAL ADDRESS08 00:00:11:2140 00:00:00:0100 PLAYER2->ALL CEC CEC REPORT PHYSICAL ADDRESS

09 00:00:11:2230 00:00:00:0600 UNREG->TUNER CEC CEC CEC PING - NACK09 00:00:11:2230 00:00:00:0600 UNREG->TUNER CEC CEC CEC PING - NACK

10 00:00:11:2830 00:00:00:0164 TUNER->ALL CEC CEC REPORT PHYSICAL ADDRESS10 00:00:11:2830 00:00:00:0164 TUNER->ALL CEC CEC REPORT PHYSICAL ADDRESS

11 00:00:11:2994 00:00:00:0600 UNREG->RECORD CEC CEC CEC PING - NACK11 00:00:11:2994 00:00:00:0600 UNREG->RECORD CEC CEC CEC PING - NACK

12 00:00:11:3594 00:00:00:0000 RECORD->ALL CEC CEC REPORT PHYSICAL ADDRESS12 00:00:11:3594 00:00:00:0000 RECORD->ALL CEC CEC REPORT PHYSICAL ADDRESS

STB-DVR ALL

STB-DVR ALL

DTV: PA 000 LA 0

AVR: PA 1000 LA 05

DVD: PA 1100 LA 04

Game System: PA 12 00 LA 08

STB-DVR: PA 1300 LA 03/LA 01

CEC Addressing – Sample Network

CEC Physical Layer

Physical Information

CEC is pin 13 on the HDMI cable. It shares a common ground with DDC.

CEC idles in a high-impedance state (the line shows a voltage between +2.5 and +3.63V).

During a message, the line will be pulled down to between 0 and +0.6V (“low-impedance”).

Physical Information (continued)

CEC supports nine devices on the bus simultaneously (potentially more if good cabling is used). The limitation is due to a network limit on capacitance of 7200pF (allowing for 100pF per device and 700pF per cable).

However, there are only 15 valid CEC logical addresses, so having a limitation of nine devices would rarely be a problem in real-world applications.

The CEC line is in use when there is a device pulling the line low. All timing is derived from the high to low transitions.

Physical Information – Bit Timing

Start Bits

Logical “0” and “1”

CEC Message Waveform

Max Rise Time = 250usecs

Max Fall Time = 50usecs

CEC Bus Control

CEC Bus Control - Retransmission

Retransmission can occur for many reasons:– A device could be holding the CEC bus low when

the initiator expects it high, causing a bus error.– A device sends a message and does not receive

the expected acknowledgement.– A device loses arbitration (retry).

Retransmission should not occur if there is sufficient indication that the follower does not support the message being sent.

CEC Bus Control - Acknowledgement

Directed messages– Intended for a single device– ACK is set as a “logical 1”– Set to “logical 0” by the follower to acknowledge

Broadcast messages– Intended for all devices– ACK is set as a “logical 1”– Must be kept as a “logical 1” by all devices– A “logical 0” is a NACK

CEC Bus Control - Acknowledgement

DTV

AVR


01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC IMAGE VIEW ON01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC IMAGE VIEW ON

02 00:00:18.41 00:00:06.20 AUDIO->ALL CEC CEC REQUEST ACTIVE SRC02 00:00:18.41 00:00:06.20 AUDIO->ALL CEC CEC REQUEST ACTIVE SRC




STB-DVR DTV

DTVAVR

high

low0.6 ms 1.5 ms

Release bus to set Ack bit to “1”

Pull down bus to Ack with “0’ bit

STB-DVRDTV

0.6 msRelease bus to set

Ack bit to “1”

AVRALL

Release bus

Do nothing toacknowledge

Directed Message

Broadcast Message

high

low

STB-DVR

CEC Bus Control – No Acknowledgement

DTV

AVR


01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC UNACKNOWLEDGED01 00:00:11.01 00:00:00.00 TUNER->TV CEC CEC UNACKNOWLEDGED

02 00:00:18.41 00:00:06.20 AUDIO->ALL CEC CEC UNACKNOWLEDGED02 00:00:18.41 00:00:06.20 AUDIO->ALL CEC CEC UNACKNOWLEDGED




STB-DVR DTV

DTVAVR

high

low0.6 ms 1.5 ms

Pull down to 0 toNack

STB-DVRDTV

Release bus

high

low0.6 msRelease bus to

set Ack bit to “1”

AVRDTV

Do nothing to Nack

Release bus to set Ack bit to “1”

Broadcast Message

Directed Message

STB-DVR

CEC Bus Control - Arbitration

Since CEC is a single wire for all devices, it is sometimes the case that two devices want to use the CEC line at the same time.

Arbitration check begins with leading edge of start bit and continues to end of initiator address.

Priority given to the device with the lowest logical address. The TV (logical address 0) has priority over all other devices.

If a device is already using the CEC line, the devices that would like to use it must wait until “signal free time” has been met (the device has stopped using the line for a defined length of time).

– At least 3 bit periods (7.2ms) in the case of a device trying to resend a message.

– At least 5 bit periods (12.0ms) for a new device wishing to send a message

– At least 7 bit periods (16.8ms) for the same device wishing to send a new message.

Signal free time is defined from the START of the final bit being sent (the high to low transition).

CEC Bus Control - Arbitration

Image View On(40 04)

DVD DTV

AVR


Active Source(4F 82 11 00)

DVD

Get Menu Language(04 91)

DTV STB-DVR

Record Status [Recording Digital Service](01 0A 02)

Record ON [Digital Service ID] (10 09 02)

01 00:00:11.01 00:00:00.00 PLAYER1->TV CEC CEC ERROR01 00:00:11.01 00:00:00.00 PLAYER1->TV CEC CEC ERROR

02 00:00:11.07 00:00:00.60 TV->PLAYER1 CEC CEC GET MENU LANGUAGE02 00:00:11.07 00:00:00.60 TV->PLAYER1 CEC CEC GET MENU LANGUAGE



Record TV ScreenRecord TV Screen (01 0F)

Image View On

05 00:00:18.41 00:00:06.20 TV->RECORDER CEC CEC UNACKNOWLEDGED05 00:00:18.41 00:00:06.20 TV->RECORDER CEC CEC UNACKNOWLEDGED

06 00:00:18.49 00:00:06.11 TV->RECORDER CEC CEC RECORD TV SCREEN06 00:00:18.49 00:00:06.11 TV->RECORDER CEC CEC RECORD TV SCREEN

07 00:00:69.51 00:00:51.10 RECORDER->TV CEC CEC RECORD ON07 00:00:69.51 00:00:51.10 RECORDER->TV CEC CEC RECORD ON

08 00:00:69.71 00:00:00.20 TV->RECORDER CEC CEC RECORD STATUS08 00:00:69.71 00:00:00.20 TV->RECORDER CEC CEC RECORD STATUS

Signal Free Time

>/= 3 bit times(~ 7.2ms)

Retransmit

Signal Free Time

>/= 5 bit times(~ 12.0ms)

New Message

DTV

Verifying CEC Implementation

Verifying the CEC Implementation

Compliance testing– In-house using compliance test tools– Plugfests (CEA and ETSI)– HDMI Authorized Test Centers

Interoperability testing (multi-vendor)– In-house – Plugfests

Verifying the CEC Implementation

Tools you will need– CEC debug tools used during development– CEC bus monitor– CEC compliance test application (Quantum Data

Test Management Environment is the recommended test tool in the HDMI CTS)

– Test fixtures

CEC Debug Testing – Error SimulatorSample screen of CEC debug test application. Enables: Simulation of acknowledgement failures Simulation of arbitration failures Ability to corrupt bits Modify timing parameters(Quantum Data CEC Controller)

CEC Debug Testing – Message LoggerSample screen of CEC Transaction logger: Logs CEC trans- actions during compliance test Logs CEC trans- actions during debug testing Shows detailed timing Shows acknowledgement and other errors(Quantum Data Auxiliary Channel Analyzer)

CEC Compliance Testing – CDF EntrySample of a CEC compliance test application showing CDF definition: Enables importing CDF from comma separated value file for fast CDF definition Enables definition of CDF parameters for new devices through GUI Supports saving CDFs for later use(Quantum Data CEC Compliance Application)

CEC Compliance Testing - Test InitiatorSample of a CEC compliance test application showing test execution: Enables running of selective tests, or groups of tests Online help for test setup Tests run automati- cally without user interaction after test setup Results provided on display interface Comprehensive report for all tests that can printed or emailed.(Quantum Data CEC Compliance Application)

For more information…

Quantum Data has prepared an educational whitepaper and a video on CEC that provides some further examples: http://www.quantumdata.com/

Thank You…

Presenter: Neal KendallTechnical consultant: Jeff Stenhouse

Animation & Graphics: Robert Watson

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