cx25870 Conexant Systems, Inc., cx25870 Datasheet - Page 141

• Manufacturer Part Number: cx25870
• Description: Video Encoder With Adaptive Flicker Filtering And Hdtv Output
• Manufacturer: Conexant Systems, Inc.

CX25870/871
Flicker-Free Video Encoder with Ultrascale Technology
3.6.1 Changes Required to Accommodate CX25870/871 in Bt868/869-Designs
Table 3-2. Relative Register Map for CX25870/871
100381B
Shared CX25870/871 &
Shared CX25870/871 &
CX25870/871 specific
CX25870/871 specific
Bt868/869 registers
Bt868/869 registers
3.6.1.1 Software
registers
register
3.6 Applications Information
The CX25870/871 is software backward compatible with Conexant’s first
generation VGA Encoder, the Bt868/869. This means that all register indices for
the Bt868/869 were carried forward to the exact same indices for the
CX25870/871. For Conexant’s second generation encoder, new registers were
added, but the actual addresses used were outside of the 0x6C to 0xD6 range
reserved for the Bt868/869 legacy functionality. Some reserved bits within the
Bt868/869 did take on significance with the CX25870/871 where necessary.
fact that the CX25870/871 can be read from using the Standard serial method as
well as the Legacy serial method. To use the Standard procedure, the master
issues CX25870’s device ID and subaddress in consecutive bytes, and the slave
acknowledges with a pulse after each transaction. Upon completion of these 2
steps, the slave transmits the final byte which contains the 8 bits of data. The
Bt868/869 cannot be read from in this manner and instead relies solely on the
Legacy method. This process is explained step-by-step in the ‘TV Auto-Detection
Procedures’ section of this specification.
power-up video output routing. The CX25870 after power-up or a signal-driven
reset transmits Video0 = composite on DAC_A, Video1 = Luma (Y) on DAC_B,
Video2 = Chroma (C) on DAC_C, and Video3 = Luma Delay on DAC_D.
Video0 = composite from DAC_A, DAC_B, and DAC_C. Reprogramming
register 0xCE correctly ensures proper video output routing.
(Must be accessed through ‘Legacy’ read procedure with ESTATUS[1:0] bits in Bt868/869)
The most significant difference in software between the two encoders is the
Another difference in terms of software between the two encoders is the
The Bt868 was different in this respect. On power-up, it sent out
(‘Standard’ or ‘Legacy’ read-back procedure ok for CX25870/871)
Register Addresses 0x28E to 0x6A (Read/Write)
Conexant
Register Addresses 0x00 to 0x04 (Read Only)
Register Address 0x6C(Read/Write)
Register Address 0xD6(Read/Write)
Register Address 0xD8(Read/Write)
Register Address 0x06(Read Only)
and
to
3.0 PC Board Considerations
3.6 Applications Information
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