AD9880SLASHPCB datasheet(20/64 Pages) AD

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AD9880

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HDMI RECEIVER

The HDMI receiver section of the AD9880 allows the reception

of a digital video stream, which is backward-compatible with

DVI and able to accommodate not only video of various for-

mats (RGB, YCrCb 4:4:4, 4:2:2), but also up to eight channels of

audio. Infoframes are transmitted carrying information about

the video format, audio clocks, and many other items necessary

for a monitor to utilize fully the information stream available.

The earlier digital visual interface (DVI) format was restricted

to an RGB 24 bit color space only. Embedded in this data

stream were Hsyncs, Vsyncs and display enable (DE) signals,

but no audio information. The HDMI specification allows

trans-mission of all the DVI capabilities, but adds several

YCrCb formats that make the inclusion of a programmable

color space converter (CSC) a very desirable feature. With this,

the scaler following the AD9880 can specify that it always

wishes to receive a particular format, for instance, 4:2:2 YCrCb

regardless of the transmitted mode. If RGB is sent, the CSC can

easily convert that to 4:2:2 YCrCb while relieving the scaler of

this task.

In addition, the HDMI specification supports the transmission

of up to eight channels of S/PDIF or I2S audio. The audio

information is packetized and transmitted during the video

blanking periods along with specific information about the

clock frequency. Part of this audio information (Audio

Infoframe) tells the user how many channels of audio, where

they should be placed, information regarding the source (make,

model), and other data.

DE GENERATOR

The AD9880 has an onboard generator for DE, for start of

active video (SAV), and for end of active video (EAV), all of

which are necessary for describing the complete data stream for

a BT656 compatible output. In addition to this particular

output, it is possible to generate the DE for cases in which a

scaler is not planned to be used. This signal alerts the following

circuitry as to which are displayable video pixels.

4:4:4 TO 4:2:2 FILTER

The AD9880 contains a filter which allows it to convert a signal

from YCrCb 4:4:4 to YCrCb 4:2:2 while maintaining the

maximum accuracy and fidelity of the original signal.

Input Color space to Output Color space

The AD9880 can accept a wide variety of input formats and

either retain that format or convert to another. Input formats

supported are

•

4:4:4 YCrCb 8 bit

•

4:2:2 YCrCb 8, 10, and 12 bit

•

RGB 8-bit

Output modes supported are

•

4:4:4 YCrCb 8 bits

•

4:2:2 YCrCb 8, 10, and 12 bits

•

Dual 4:2:2 YCrCb 8 bits.

Color space Conversion (CSC) Matrix

The color space conversion (CSC) matrix in the AD9880

consists of three identical processing channels. In each channel,

three input values are multiplied by three separate coefficients.

Also included are an offset value for each row of the matrix and

a scaling multiple for all values. Each value has a 13 bit twos

complement resolution to ensure the signal integrity is main-

tained. The CSC is designed to run at speeds up to 150 MHz

supporting resolutions up to 1080 p at 60 Hz. With any-to-any

color space support, formats such as RGB, YUV, YCbCr, and

others are supported by the CSC.

The main inputs, Rin, Gin, and Bin come from the 8- to 12-bit

inputs from each channel. These inputs are based on the input

format detailed in Table 7 to Table 15. The mapping of these

inputs to the CSC inputs is shown in Table 9.

Table 9. CSC Port Mapping

Input Channel

CSC Input Channel

R/CR

RIN

Gr/Y

GIN

B/CB

One of the three channels is represented in Figure 13. In each

processing channel the three inputs are multiplied by three

separate coefficients marked a1, a2, and a3. These coefficients

are divided by 4096 to obtain nominal values ranging from

–0.9998 to +0.9998. The variable labeled a4 is used as an offset

control. The CSC_mode setting is the same for all three

processing channels. This multiplies all coefficients and offsets

by a factor of 2csc_mode.

The functional diagram for a single channel of the CSC as

shown in Figure 13 is repeated for the remaining G and B

channels. The coefficients for these channels are b1, b2, b3, b4,

c1, c2, c3, and c4.

×2

a1[12:0]

a2[12:0]

a3[12:0]

RIN [11:0]

BIN [11:0]

GIN [11:0]

×4

CSC_MODE[1:0]

a4[12:0]

ROUT [11:0]

4096

Figure 13. Single CSC Channel

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