HMP8156 データシートの表示（PDF） - Intersil

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HMP8156

NTSC/PAL Encoder

Intersil 

HMP8156

Functional Operation

The HMP8156 is a fully integrated digital encoder. It accepts

digital video input data and generates four analog video out-

put signals. The input data format is selectable and includes

YCbCr, RGB, and overlay data. The outputs are config-

urable to be either two composite video signals and Y/C (S-

Video) or one composite and component RGB video.

The HMP8156 accepts pixel data in one of several formats

and transforms it into 4:4:4 sampled luminance and chromi-

nance (YCbCr) data. If enabled, the encoder also mixes

overlay data with the input data. The encoder then interpo-

lates the YCbCr data to twice the pixel rate and low pass fil-

ters it to match the bandwidth of the video output format. If

enabled, the encoder also adds Closed Captioning informa-

tion to the Y data. At the same time, the encoder modulates

the chrominance data with a digitally synthesized subcarrier.

Finally, the encoder outputs the luminance, chrominance,

and their sum as analog signals using 10-bit D/A converters.

The HMP8156 provides operating modes to support all ver-

sions of the NTSC and PAL standards and accepts full and

SIF size input data with rectangular (ITU-R BT.601) and

square pixel ratios. It operates from a single clock at twice

the pixel clock rate determined by the operating mode.

The HMP8156’s video timing control is flexible. It may oper-

ate as the master generating the system’s video timing con-

trol signals or it may accept external timing controls. The

polarity of the timing controls and the number of active pixels

and lines are programmable.

Pixel Data Input Formats

The HMP8156 accepts pixel data via the P0-P23 input pins.

The definition of each pixel input pin is determined by the

input format selected in the input format register. The defini-

tion for each mode is shown in Table 2.

YCbCr Pixel Data

The HMP8156 accepts 4:2:2 sampled YCbCr input data.

The luminance and color difference signals are each 8 bits,

scaled 0 to 255. Values outside their nominal ranges (16-

235 for Y and 16-240 for Cb and Cr) are processed normally.

The color difference signals are time multiplexed into one 8-

bit bus beginning with a Cb sample. The Y and CbCr busses

may be input in parallel (16-bit mode) or may be time multi-

plexed and input as a single bus (8-bit mode). The single

bus may also contain SAV and EAV video timing reference

codes (ITU-R BT.656 mode).

RGB Data

The HMP8156 accepts 4:4:4 sampled RGB component

video input data. The color signals may be (8,8,8) for 24-bit

mode or (5,6,5) for 16-bit mode. In 24-bit mode, they are

scaled 0 to 255, black to white. In 16-bit mode, the encoder

left shifts the input so that it has the same scale as 24-bit

input. The RGB data may be linear or gamma corrected; if

enabled, the encoder will gamma correct the input data.

Overlay Data

The HMP8156 accepts 5 bits of pixel overlay input data and

combines it with the input pixel data. The data specifies an

overlay color and the fractions of the new and original colors

to be summed.

Blue Screen Generation

In blue screen mode, the HMP8156 ignores the pixel input

data and generates a solid, blue screen. The overlay inputs

may be used to place information over the blue screen.

Input Processing

pixel basis. The overlay color palette is shown in Table 1.

COLOR SPACE CONVERSION

TABLE 1. OVERLAY COLOR PALETTE

For linear RGB input formats, the encoder applies gamma-

correction using a selectable gamma value of 1/2.2 or 1/2.8.

The gamma-corrected RGB data from either the correction

function in linear mode or the input port otherwise is con-

verted to 4:4:4 sampled YCbCr data.

For the YCbCr input formats, the encoder converts the 4:2:2

sampled data to 4:4:4 sampled data. The conversion is done

by 2x upsampling the Cb and Cr data. The upsampling func-

tion uses linear interpolation.

OVERLAY PROCESSING

OL2-OL0

000

001

010

011

100

101

110

111

COLOR

Pixel Data

75% Blue

75% Red

75% Magenta

75% Green

75% Cyan

75% Yellow

100% White

Note that overlay capability is not available when the 24-bit

RGB input format is used.

The HMP8156 accepts overlay data via the OL0-OL2, M0,

and M1 pins. Overlay mixing is done using the 4:4:4 YCbCr

pixel data from the color space converter. The YCbCr data

following overlay processing is used as input data by the

video processing functions.

The OL0-OL2 inputs select the color to be mixed with the

pixel data. Overlay colors 1-7 are standard color bar colors.

Overlay color 0 is special and disables mixing on a pixel by

The encoder provides 4 methods for mixing the overlay data

with the pixel data: disabled, external mixing, internal mixing

and no mixing. The method used is selected in the input for-

mat control register.

Overlay Mixing: Disabled

When overlay mixing is disabled, the OL0-OL2, M0, and M1

inputs are ignored and the pixel data is not changed.

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