AD9882 Просмотр технического описания (PDF) - Analog Devices

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AD9882

Dual Interface for Flat Panel Displays

Analog Devices 

AD9882

POWER SUPPLY

VD

Main Power Supply

It should be as quiet as possible.

PVD

PLL Power Supply

It should be as quiet as possible.

VDD

Outputs Power Supply

The power for the data and clock outputs. It can

run at 3.3 V or 2.5 V.

GND

Ground

The ground return for all circuitry on the device.

It is recommended that the application circuit

board have a single, solid ground plane.

THEORY OF OPERATION (DIGITAL INTERFACE)

Capturing of the Encoded Data

The first step in recovering the encoded data is to capture the raw

data. To accomplish this, the AD9882 employs a high speed phase

locked loop (PLL) to generate clocks capable of oversampling

the data at the correct frequency. The data capture circuitry

continuously monitors the incoming data during horizontal and

vertical blanking times (when DE is low) and selects the best

sampling phase for each data channel independently. The phase

information is stored and used until the next blanking period

(one video line).

Data Frames

The digital interface data is captured in groups of 10 bits each,

which are called data frames. During the active data period,

each frame is made up of the nine encoded video data bits and

one dc balancing bit. The data capture block receives this

data serially but outputs each frame in parallel 10-bit words.

Special Characters

During periods of horizontal or vertical blanking time (when DE is

low), the digital transmitter will transmit special characters. The

AD9882 will receive these characters and use them to set the video

frame boundaries and the phase recovery loop for each chan-

nel. There are four special characters that can be received.

They are used to identify the top, bottom, left side, and right

side of each video frame. The data receiver can differentiate

these special characters from active data because the special

characters have a different number of transitions per data frame.

Channel Resynchronization

The purpose of the channel resynchronization block is to

resynchronize the three data channels to a single internal data

clock. Coming into this block, all three data channels can be on

different phases of the 3¥ oversampling PLL clock (0∞, 120∞,

and 240∞). This block can resynchronize the channels from a

worst-case skew of one full input period (8.93 ns at 112 MHz).

Data Decoder

The data decoder receives frames of data and sync signals from

the data capture block (in 10-bit parallel words) and decodes

them into groups of eight RGB bits, two control bits, and a data

enable bit (DE).

HDCP

The AD9882 contains all the circuitry necessary for decryption

of a high bandwidth digital content protection encoded DVI

video stream. A typical HDCP implementation is shown in

Figure 10. Several features of the AD9882 make this possible

and add functionality to ease the implementation of HDCP.

The basic components of HDCP are included in the AD9882.

A slave serial bus connects to the DDC clock and DDC data

pins on the DVI connector to allow the HDCP enabled DVI

transmitter to coordinate the HDCP algorithm with the AD9882.

A second serial port (MDA/MCL) allows the AD9882 to read

the HDCP keys and key selection vector (KSV) stored in an

external serial EEPROM. When transmitting encrypted video,

the DVI transmitter enables HDCP through the DDC port.

The AD9882 then decodes the DVI stream using information

provided by the transmitter, HDCP keys, and KSV.

The AD9882 allows the MDA and MCL pins to be three-stated

using the MDA/MCL three-state bit (Register 1B, Bit 7) in the

configuration registers. The three-state feature allows the EEPROM

to be programmed in-circuit. The MDA/MCL port must be

three-stated before attempting to program the EEPROM using

an external master. The keys will be stored in an I2C compatible

3.3 V serial EEPROM of at least 512 bytes in size. The EEPROM

should have a device address of A0H.

Proprietary software licensed from Analog Devices encrypts

the keys and creates properly formatted EEPROM images for

use in a production environment. Encrypting the keys helps

maintain the confidentiality of the HDCP keys as required by

the HDCP v1.0 specification. The AD9882 includes hard-

ware for decrypting the keys in the external EEPROM.

ADI will provide a royalty free license for the proprietary

software needed by customers to encrypt the keys between

the AD9882 and the EEPROM only after customers provide

evidence of a completed HDCP Adopter’s license agreement

and sign ADI’s software license agreement. The Adopter’s

license agreement is maintained by Digital Content Protection,

LLC, and can be downloaded from www.digital-cp.com.

To obtain ADI’s software license agreement, contact the Display

Electronics Product Line directly by sending an email to

flatpanel_apps@analog.com.

DVI

CONNECTOR

DDC CLOCK

DDC DATA

3.3V

5k⍀ PULL-UP

RESISTORS

DDC SCL

MCL

AD9882

DS

DDC SDA

3.3V

150⍀ SERIES

RESISTORS

MDA

3.3V

5k⍀ PULL-UP

RESISTORS

SCL

EEPROM

SDA

Figure 10. HDCP Implementation Using the AD9882

–20–

REV. A

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