bt865a Conexant Systems, Inc., bt865a Datasheet - Page 63

• Manufacturer Part Number: bt865a
• Description: Ycrcb To Ntsc/pal Digital Video Encoder
• Manufacturer: Conexant Systems, Inc.

Bt864A/Bt865A Data Sheet
3.6
3.6.1
Figure 3-5. I
100138C
02/17/03
Footnote:
(1)
Acknowledge generated by Bt864A/865A.
SDA
SCL
2
C Diagram
I
Data Transfer on the I
1
2
C Programming
2
3
Main Address
clock can generate significant energy at the aural carrier frequency. In the case of
hard-edged, unblended characters having a font cell size which is a multiple of three
pixels, harmonic energy at the aural carrier frequency may be only 15 dB below the
maximum video level, or roughly equal to the power of the sound subcarrier in the RF
spectrum.
Trap attenuation of about 20 dB can assure that the resultant interference with the FM
aural signal will degrade the noise level at the monaural decoded receiver about 1 dB
(–44 dB range) with less than 50 ns additional chroma delay [Multichannel stereo
(e.g., BTSC) or Second Audio Program (SAP) encoder may require greater
attenuation due to lower level subcarriers]. Therefore, luminance delay compensation
of about 225 ns on just the RF feed (e.g. CVBS/B) can correct for the chroma delay
artifacts of additional processing in the RF channel without compromising the
inherently low group delay distortion of the baseband channels (e.g. CVBS/Y/C).
An I
provides farther information on I
between SDA and SCL to be used when programming the I
being used, both SDA and SCL lines must be left high.
Every byte put onto the SDA line should be 8 bits long (MSB first), followed by an
acknowledge bit, which is generated by the receiving device.
Each data transfer is initiated with a start condition and ended with a stop condition.
The first byte after a start condition is always the address byte. If this is the device’s
own address, the device will generate an acknowledge by pulling the SDA line low
4
2
5
C reference manual has been developed and may be obtained upon request. This
6
7
8
(1)
9
1
2
2
C Bus
Conexant
3
Subaddress
4
5
2
C bus protocol.
6
7
8
(1)
9
1
Subsequent Bytes and Acknowledge
Interpreted as Data Values for
Autoincremented Subaddress Locations
2
Figure 3-5
3
4
Data
5
2
C bus. If the bus is not
6
shows the relationship
7
8
PC Board Considerations
(1)
9
100138_033
3-9