ADV7181BBCPZ datasheet(31/96 Pages) AD

31 / 96 page

ADV7181B

Rev. 0 | Page 31 of 96

For example, program the ADV7181B into manual fixed gain

mode with a desired gain of 0.89.

Use Equation 1 to convert the gain:

0.89 × 2048 = 1822.72

Truncate to integer value:

1822.72 = 1822

Convert to hexadecimal:

1822d = 0x71E

Split into two registers and program:

Luma Gain Control 1 [3:0] = 0x7

Luma Gain Control 2 [7:0] = 0x1E

Enable Manual Fixed Gain Mode:

Set LAGC[2:0] to 000

BETACAM Enable Betacam Levels, Address 0x01 [5]

If YPrPb data is routed through the ADV7181B, the automatic

gain control modes can target different video input levels, as

outlined in Table 41. Note that the BETACAM bit is valid only if

the input mode is YPrPb (component). The BETACAM bit

basically sets the target value for AGC operation.

A review of the following sections is useful:

•

SETADC_sw_man_en, Manual Input Muxing Enable,

Address C4 [7] to find how component video (YPrPb) can

be routed through the ADV7181B.

•

Video Standard Selection to select the various standards,

for example, with and without pedestal.

The automatic gain control (AGC) algorithms adjust the levels

based on the setting of the BETACAM bit (see Table 35.).

Table 35. BETACAM Function

BETACAM

Description

0 (default)

Assuming YPrPb is selected as input format.

Selecting PAL with pedestal selects MII.

Selecting PAL without pedestal selects SMPTE.

Selecting NTSC with pedestal selects MII.

Selecting NTSC without pedestal selects SMPTE.

Assuming YPrPb is selected as input format.

Selecting PAL with pedestal selects BETACAM.

Selecting PAL without pedestal selects BETACAM

variant.

Selecting NTSC with pedestal selects BETACAM.

Selecting NTSC without pedestal selects BETACAM

variant.

PW_UPD Peak White Update, Address 0x2B [0]

The peak white and average video algorithms determine the

gain based on measurements taken from the active video. The

PW_UPD bit determines the rate of gain change. LAGC[2:0]

must be set to the appropriate mode to enable the peak white or

average video mode in the first place. For more information,

refer to the LAGC[2:0] Luma Automatic Gain Control, Address

0x30 [7:0] section.

Setting PW_UPD to 0 updates the gain once per video line.

Setting PW_UPD to 1 (default) updates the gain once per field.

Chroma Gain

CAGC[1:0] Chroma Automatic Gain Control,

Address 0x2C [1:0]

The two bits of Color Automatic Gain Control mode select the

basic mode of operation for automatic gain control in the

chroma path.

Table 36. CAGC Function

CAGC[1:0]

Description

Manual fixed gain (use CMG[11:0]).

Use luma gain for chroma.

10 (default)

Automatic gain (based on color burst).

Freeze chroma gain.

CAGT[1:0] Chroma Automatic Gain Timing,

Address 0x2D [7:6]

The Chroma Automatic Gain Timing register allows the user to

influence the tracking speed of the chroma automatic gain

control. This register has an effect only if the CAGC[1:0]

Table 37. CAGT Function

CAGT[1:0]

Description

Slow (TC = 2 sec)

Medium (TC = 1 sec)

Fast (TC = 0.2 sec)

11 (default)

Adaptive

Table 38. Betacam Levels

Name

Betacam (mV)

Betacam Variant (mV)

SMPTE (mV)

MII (mV)

Y Range

0 to 714 (incl. 7.5% pedestal)

0 to 714

0 to 700

0 to 700 (incl. 7.5% pedestal)

Pb and Pr Range

–467 to +467

–505 to +505

–350 to +350

–324 to +324

Sync Depth

286

300

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