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ADV7181 Datasheet(PDF) 34 Page - Analog Devices |
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ADV7181 Datasheet(HTML) 34 Page - Analog Devices |
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34 / 104 page  ADV7181 Rev. B | Page 34 of 104 CG[11:0] Chroma Gain, Address 0x2D [3:0]; Address 0x2E [7:0] CMG[11:0] Chroma Manual Gain, Address 0x2D [3:0]; Address 0x2E [7:0] Chroma gain [11:0] is a dual-function register: • If written to, a desired manual chroma gain can be programmed. This gain becomes active if the CAGC[1:0] mode is switched to manual fixed gain. • Refer to Equation 2 for calculating a desired gain. • If read back, this register returns the current gain value. Depending on the setting in the CAGC[1:0] bits, this is one of the following values: o Chroma manual gain value (CAGC[1:0] set to chroma manual gain mode). o Chroma automatic gain value (CAGC[1:0] set to any of the automatic modes). Table 71. CG/CMG Function CG[11:0]/CMG[11:0] Read/Write Description CMG[11:0] Write Manual gain for chroma path. CG[11:0] Read Currently active gain. () 4 ... 0 1024 4095 0 _ = ≤ < = CG Gain Chroma (2) Example Freezing the automatic gain loop and reading back the CG[11:0] register results in a value of 0x47A. 1. Convert the read back value to decimal: 0x47A = 1146d 2. Apply Equation 2 to convert the readback value: 1146/1024 = 1.12 CKE Color Kill Enable, Address 0x2B [6] The Color Kill Enable bit allows the optional color kill function to be switched on or off. For QAM-based video standards (PAL and NTSC) as well as FM-based systems (SECAM), the threshold for the color kill decision is selectable via the CKILLTHR[2:0] bits. If color kill is enabled, and if the color carrier of the incoming video signal is less than the threshold for 128 consecutive video lines, color processing is switched off (black and white output). To switch the color processing back on, another 128 consecutive lines with a color burst greater than the threshold are required. The color kill option only works for input signals with a modu- lated chroma part. For component input (YPrPb), there is no color kill. Table 72. CKE Function CKE Description 0 Color kill disabled. 1 (default) Color kill enabled. CKILLTHR[2:0] Color Kill Threshold, Address 0x3D [6:4] The CKILLTHR[2:0] bits allow the user to select a threshold for the color kill function. The threshold only applies to QAM- based (NTSC and PAL) or FM modulated (SECAM) video standards. To enable the color kill function, the CKE bit must be set. For settings 000, 001, 010, and 011, chroma demodulation inside the ADV7181 may not work satisfactorily for poor input video signals. Table 73. CKILLTHR Function Description CKILLTHR[2:0] SECAM NTSC, PAL 000 No color kill Kill at < 0.5% 001 Kill at < 5% Kill at < 1.5% 010 Kill at < 7% Kill at < 2.5% 011 Kill at < 8% Kill at < 4.0% 100 (default) Kill at < 9.5% Kill at < 8.5% 101 Kill at < 15% Kill at < 16.0% 110 Kill at < 32% Kill at < 32.0% 111 Reserved for ADI internal use only. Do not select. |
Similar Part No. - ADV7181_15 |
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Similar Description - ADV7181_15 |
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