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CIP3250A

Component Interface Processor

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ADVANCE INFORMATION

CIP 3250A

2. Functional Description

This section describes the functionality of the various

blocks shown in the block diagram of Fig. 2–1 in detail.

The CIP 3250A is controlled via an I2C bus interface. For

information regarding how to program the registers of

the CIP 3250A, please refer to the register list (see

Tables 2–9 and 2–10). The I2C bus interface uses sub-

addressing to access the register. In the following, I2C

registers are referenced by the sub-addresses given in

parenthesis; for example, I2C register <9>. To interface

correctly, a pin description for the CIP 3250A is given in

section 3.3.

2.1. Analog Front End

– SCART-level inputs (RGB/YUV and

Fast Blank = 1.0 Vpp, Fast Blank must be ext. clipped)

– triple 8-bit ADC for RGB/YUV

– 6 bit ADC for Fast Blank

– sampling rate 13.5 to 20.25 MHz

– no sync separation included

All analog video input signals and the analog Fast Blank

signal must be band limited to 5 MHz before analog to

digital conversion.

The CIP 3250A can process either analog YUV input

signals or analog RGB input signals which are AC-

coupled with a nominal input voltage level of 700 mV +

3 dB (1 VPP). There is no circuitry implemented for inter-

nal sync separation. Input voltage range of the Fast

Blank signal is 0 to 1 V. The Fast Blank input signal is

DC-coupled.

2.2. Clamping

– internal clamping for RGB and YUV with adjustable

start and width

– black level reference only during horizontal and verti-

cal blanking interval on RGB/YUV inputs

– no proper clamping if sync is on G

In RGB mode, clamping takes place on black level (digi-

tal 16 or 8) using a clamping window as described below.

In YUV mode, clamping is done on black level (digital 16)

for Y (luma) and on saturation level zero (digital 128) for

UV (chroma) using a clamping window. Select between

RGB mode and YUV mode via I2C register <09>YUV.

The black level reference value (digital 16 or 8) can be

selected via I2C register <09>CLMPOFS. In a standard

DIGIT 2000 application without a conversion of Y (luma)

to ITUR code levels at the digital inputs (see section 2.9.

<10>YLEVEL), convert the black level to digital 32 via

I2C register <04>CLSEL.

The clamping window is programmable in reference to

the H-sync signal (see Fig. 2–13) by a start and stop val-

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ue via I2C registers <18> and <19>. A window size of 32

or 64 sample clocks is recommended. Clamping is dis-

abled if start and stop values are equal after reset. Once

enabled it can not be switched off. Using a coupling ca-

pacitor of 220 nF, a hum of approximately 400 mV at

50 Hz can be compensated.

2.3. Matrix

– matrix RGB ⇒ Y(R–Y)(B–Y):

Y = 0.299*R + 0.587*G + 0.114*B

(R–Y) = 0.701*R – 0.587*G – 0.114*B

(B–Y) = –0.299*R – 0.587*G + 0.886*B

– fixed coefficients with a resolution of 8 bits.

– matrix enable/disable for analog RGB/YUV input pro-

grammable via I2C register

The matrix of the CIP 3250A converts the digitized RGB

signals to the intermediate signals Y, R–Y, and B–Y. En-

able the matrix via I2C register <04>MAON. The inter-

mediate signals at the output of the matrix can be con-

verted to YUV signals of the DIGIT 2000 system or to

YCrCb of the DIGIT 3000 system by the YUV control (see

section 2.4.). To omit conversion from RGB to

Y(R–Y)(B–Y), switch off the matrix and the CTBRST

block via I2C register <04>MAON and <04>CBSON.

2.4. YUV Control (on RGB-path only )

– Y contrast (ct) and brightness (br) with rounding or

noise shaping and limiting to 8 bit:

Y = Y*ct + br

ct = 0 ... 63/32 in 64 steps

br = –128 ... +127 in 256 steps

– UV saturation (sat) with rounding or noise shaping and

limiting to 8 bit (controllable by CCU via I2C bus):

UEXT = (B–Y) * Usat

VEXT = (R–Y) * Vsat

Usat,Vsat = 0 ... 63/32 in 64 steps

(UINT = [0.5*(B–Y)] * Usat

VINT = [0.875*(R–Y)] * Vsat)

Within the CTBRST block, switched on via I2C register

<04>CBSON, two different options can be used to con-

vert from (R–Y)(B–Y) to UV (PAL standard). In internal

mode (UVINT), conversion to PAL standard is done be-

fore the multiplication of the contents of the saturation

registers. Using the external mode (UVEXT) of

<04>SMODE, the user has to implement the conversion

factors via the two saturation registers (Usat, Vsat).

Since the two saturation registers can be programmed

separately, it is also very easy to convert to YCrCb (Stu-

dio standard) of the DIGIT 3000 system.

Contrast, brightness, and saturation can be adjusted for

the video signals of the analog input via I2C registers

<00> to <03>. A functional description of this circuit can

be found in figures 2–2 and 2–3 respectively.

To improve the amplitude resolution of the luma (Y) and

chroma (UV) video signals after multiplication with the

7

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