cx25840 Conexant Systems, Inc., cx25840 Datasheet - Page 58

• Manufacturer Part Number: cx25840
• Description: Video Decoder And Broadcast Audio
• Manufacturer: Conexant Systems, Inc.

Detailed Functional Description
3.4.11
3.4.12
3-32
Timing Generator
Copy Protection Detect
The copy protection logic detects the presence of the pseudo-sync pulses and color
striping in the video waveform according to the Macrovision copy protection
detection specification. If more than a minimum specified number of pseudo-sync
pulses (PSP) in a field are detected, the MV_PSP status bit is set in the Copy
Protection Status register (0x40C). If Macrovision color striping is detected for more
than a specified minimum number of lines, the logic sets a status bit indicating that
color striping has been detected and additional status bits indicating what type of color
striping is detected, type 2 or type 3. The MV_CS bit indicates the presence of color
striping, the MV_T3CS bit indicates the presence of type 3 color striping, and
MV_TYPE2_PAIR indicates a type 2 pair detected. These status bits can be found in
the Copy Protection Status register (0x40C).
Additionally, the pseudo-sync pulse and color striping status indicators are encoded to
form a 2-bit Macrovision Copy Control status as described in the Macrovision
detection specification. This code is represented by the MV_CDAT bits in the Copy
Protection Status register (0x40C). The host processor can be automatically informed
of changes in the presence of copy protection on the source material through the
interrupt pin. A MV_CHANGE_STAT interrupt status with mask is available in the
Interrupt Status 2 and Interrupt Mask 2 registers (0x411 and 0x413), respectively. If
the MV_CHANGE_STAT mask is 0, any change to the status bit is reflected on the
interrupt pin. This alleviates the host processor from having to continually poll the
status register to see if copy protection is present on the incoming video waveform.
The timing generator provides all the timing control strobes for video decoder paths
that follow the sample rate converter block. It outputs both horizontal and vertical
timing control, including blanking and burst gate control. The SRC module provides
vertical sync (VSYNC) and horizontal sync (HSYNC) reference pulses to
synchronize the timing generator.
In auto-detect mode, the timing generator is also responsible for controlling the
format search. Based on the lines-per-frame count, the subcarrier frequency, and the
presence of phase alternation, the mode is selected. When video lock is lost and re-
acquired, the default assumption is that the video broadcast standard remains
unchanged. It is only when differences in the key format metrics are detected that the
format selection is changed.
Upon selecting a mode, the timing generator automatically sets all of the timing
parameters required for the selected video broadcast standard. There is also a manual
mode where the timing parameters are produced directly from the programmable
register set.
Conexant
CX25840/1/2/3 Data Sheet
102284B
8/3/05