TFP503

PanelBus HDCP DIGITAL RECEIVER

SLDS149 − AUGUST 2004

12

POST OFFICE BOX 655303

fundamental operation

The TFP503 is a DVI-compliant digital receiver that is used in digital display systems to receive and decode

transition-minimized differential-signaling (T.M.D.S.) encoded RGB pixel data streams. High-bandwidth digital

content protection (HDCP) receiver functionality provides decryption of the DVI input data streams encrypted

at the transmitter, such as TI’s HDCP TFP510 or TFP513 transmitter, to prevent unauthorized viewing or

copying of digital content. In a digital display system, a host, usually a PC or consumer electronics device,

contains a DVI-compatible transmitter that receives 24-bit pixel data along with the appropriate control signals.

The HDCP TFP510 or TFP513 transmitter encrypts and encodes the signals into a high-speed, low-voltage,

differential serial bit stream optimized for transmission over a twisted-pair cable to a display device. The display

device, usually a flat-panel monitor, requires a DVI- and HDCP-compatible receiver like the TI TFP503 to

decode and decrypt the serial bit stream back to the same 24-bit pixel data and control signals that originated

at the host. This decoded data can then be applied directly to the flat panel drive circuitry to produce an image

on the display. Since the host and display can be separated by distances up to five meters or more, serial

transmission of the pixel data is preferred. To support modern display resolutions up to UXGA, a high-bandwidth

receiver with good jitter and skew tolerance is required.

The TFP503 incorporates high-bandwidth digital content protection (HDCP). This provides secure data

transmission for high-definition video. The TFP503 comes with embedded preprogrammed HDCP keys, thus

eliminating the need both for an external storage device to store the HDCP keys and for the customer to

purchase HDCP keys from the licensing authority. An encryption scheme ensures that the embedded HDCP

keys are encrypted, thus providing highest level of key security.

T.M.D.S. pixel data and control signal encoding

Only one of two possible T.M.D.S. characters for a given pixel is transmitted at a given time. The transmitter

keeps a running count of the number of 1s and 0s previously sent, transmits the character that minimizes the

number of transitions, and approximates a dc balance of the transmission line.

Three T.M.D.S. channels receive RGB pixel data during active display time, DE = high. These same three

channels also receive HSYNC, VSYNC, CTL3, and two user-definable control signals, CTL[2:1], during inactive

display or blanking interval (DE = low). The following table maps the received input data to the appropriate

T.M.D.S. input channel in a DVI-compliant system.

RECEIVED PIXEL DATA

ACTIVE DISPLAY DE = HIGH

T.M.D.S. INPUT CHANNEL

OUTPUT TERMINALS

(VALID FOR DE = HIGH)

Red[7:0]

Channel-2 (Rx2

±)

QE[23:16] QO[23:16]

Green[7:0]

Channel-1 (Rx1

±)

QE[15:8] QO[15:8]

Blue[7:0]

Channel-0 (Rx0

±)

QE[7:0] QO[7:0]

RECEIVED CONTROL DATA

BLANKING DE = LOW

T.M.D.S. INPUT CHANNEL

OUTPUT TERMINALS

(VALID FOR DE = LOW)

CTL[3:2] (see Note 14)

Channel-2 (Rx2

±)

CTL2

CTL[1:0] (see Note 14)

Channel-1 (Rx1

±)

CTL1

HSYNC, VSYNC

Channel-0 (Rx0

±)

HSYNC, VSYNC

NOTE 14: Some DVI transmitters transmit a CTL0 signal. The TFP503 decodes and transfers CTL[2:1] and ignores CTL0 characters. CTL3

is used internally to enable HDCP decryption. CTL3 and CTL0 are not available as TFP503 outputs.

The TFP503 discriminates between valid pixel T.M.D.S. characters and control T.M.D.S. characters to

determine the state of active display vs blanking, i.e., state of DE.

high-bandwidth digital content protection (HDCP) overview

TI’s HDCP transmitters and receivers use up to three cipher engines to protect information that may be

externally accessible to the user.