Inside HDMI (High Definition Multimedia Interface)

Connectors

HDMI has two kinds of connectors: type A, with 19 pins, and Type B, with 29 pins. This second connector is bigger and allows the use of dual-link configuration, which doubles the maximum transfer rate that can be used. With a type A connector it is possible to achieve a pixel clock up to 165 MHz (using the architecture shown in Figure 1) while with a type B connector it is possible to achieve a pixel clock rate up to 330 MHz (doubling the architecture shown in Figure 1).

HDMIFigure 2: Type A HDMI connector vs. DVI connector.

TMDS standard limits the cable length to 50 feet (15 meters).

Transmitting devices with a type A plug can be connected to receiving devices with a type B plug using a cable with a type A plug at one end and a type B plug at the other. It is not possible to connect a transmitting device with a type B plug to a receiving device with a type A plug.

As we mentioned earlier, HDMI and DVI are compatible and there are converter cables available.

On the tables below we list the pinout for the type A and type B connectors and also the pinout for the DVI/HDMI converter cable. But first let’s talk something interesting about pricing.

Pricing

One interesting thing about HDMI is that it isn’t an open standard. Manufacturers willing to use it must pay royalties to HDMI Licensing, LLC: an annual fee of USD 15,000 and USD 0,15 per each device using HDMI sold. This rate drops to USD 0,05 if the manufacturer uses HDMI logo on the product and on its promotional material. If HDCP is implemented, the royalty fee drops to USD 0,04 per unit sold.

Also, if the manufacturers want to use HDCP copy-protection mechanism, they must pay an annual fee of USD 15,000 plus USD 0,005 per device key purchased, which must be paid to Digital Content Protection, LLC (a company owned by Intel).

More information about HDMI can be found on http://www.hdmi.org and more information about HDCP can be found at http://www.digital-cp.com.

Cables and Connectors Pinout

Type A HDMI Connector

Pin Signal
1 TMDS Data2+
2 TMDS Data2 Shield
3 TMDS Data2
4 TMDS Data1+
5 TMDS Data1 Shield
6 TMDS Data1–
7 TMDS Data0+
8 TMDS Data0 Shield 
9 TMDS Data0–
10 TMDS Clock+
11 TMDS Clock Shield
12 TMDS Clock–
13 CEC
14 Reserved (N.C. on device)
15 SCL
16 SDA
17 DDC/CEC Ground
18 + 5V
19 Hot Plug Detect

Type B HDMI Connector

Pin Signal
1 TMDS Data2+
2 TMDS Data2 Shield
3 TMDS Data2-
4 TMDS Data1+
5 TMDS Data1 Shield
6 TMDS Data1-
7 TMDS Data0+
8 TMDS Data0 Shield
9 TMDS Data0-
10 TMDS Clock+
11 TMDS Clock Shield
12 TMDS Clock-
13 TMDS Data5+
14 TMDS Data5 Shield
15 TMDS Data5-
16 TMDS Data4+
17 TMDS Data4 Shield
18 TMDS Data4-
19 TMDS Data3+
20 TMDS Data3 Shield
21 TMDS Data3-
22 CEC
23 Reserved (N.C. on device)
24 Reserved (N.C. on device)
25 SCL
26 SDA
27 DDC/CEC Ground
28 +5V
29 Hot Plug Detect

Type A HDMI Connector x DVI-D

HDMI Pin Signal Wire DVI-D Pin
1 TMDS Data2+ A 2
2 TMDS Data2 Shield B 3
3 TMDS Data2- A 1
4 TMDS Data1+ A 10
5 TMDS Data1 Shield B 11
6 TMDS Data1- A 9
7 TMDS Data0+ A 18
8 TMDS Data0 Shield B 19
9 TMDS Data0- A 17
10 TMDS Clock+ A 23
11 TMDS Clock Shield B 22
12 TMDS Clock- A 24
13 CEC N.C. N.C.
14 Reserved N.C. N.C.
15 SCL C 6
16 DDC C 7
17 DDC/CEC Ground D 15
18 +5V 5V 14
19 Hot Plug Detect C 16
20 Not Connected   4
21 Not Connected   5
22 Not Connected   12
23 Not Connected   13
24 Not Connected   20
25 Not Connected   21
26 Not Connected   8

Type B HDMI Connector x DVI-D

HDMI Pin Signal Wire DVI-D Pin
1 TMDS Data2+ A 2
2 TMDS Data2 Shield B 3
3 TMDS Data2- A 1
4 TMDS Data1+ A 10
5 TMDS Data1 Shield B 11
6 TMDS Data1- A 9
7 TMDS Data0+ A 18
8 TMDS Data0 Shield B 19
9 TMDS Data0- A 17
10 TMDS Clock+ A 23
11 TMDS Clock Shield B 22
12 TMDS Clock- A 24
13 TMDS Data5+ A 21
14 TMDS Data5 Shield B 19
15 TMDS Data5- A 20
16 TMDS Data4+ A 5
17 TMDS Data4 Shield B 3
18 TMDS Data4- A 4
19 TMDS Data3+ A 13
20 TMDS Data3 Shield B 11
21 TMDS Data3- A 12
22 CEC N.C. N.C.
23 Reserved N.C. N.C.
24 Reserved N.C. N.C.
25 SCL C 6
26 DDC C 7
27 DDC/CEC Ground D 15
28 +5V 5V 14
29 Hot Plug Detect C 16
  Not Connected N.C. 8

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Author: Gabriel Torres

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.

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