CX25870/871
1.0 Functional Description
Flicker-Free Video Encoder with Ultrascale Technology
1.3 Device Description
Table 1-27. Common Registers Required to Switch CX25870/25871 into EIA-770.2-A- or EIA-770.1-Compliant Component
Video Outputs
Register/Bit Name
Location
Value
Comment
MCOMPY[7:0]
MCOMPU[7:0]
Bits 7:0 – Register 3C
Bits 7:0 – Register 3E
80 (hex)
90 (hex)
Gain multiplication factor for Y analog output.
Gain multiplication factor for PB analog output.
MCOMPV[7:0]
SETUP
Bits 7:0 – Register 40
Bit 1 - Register A2
66 (hex)
Gain multiplication factor for PR analog output.
1 (binary)
Required for EIA770.1 compliance. Enables 7.5 IRE
pedestal normally present within NTSC-M active video
lines.
OUT_MODE[1:0]
Bits 3:2 - Register D6
10 (binary)
Enables Component Video output mode. CX25870
DACs will transmit Video[0-3] as EIA-770.2-A or 770.1
compliant
PR / Y / PB / Y_DELAY outputs.
OUT_MUXA[1:0]
OUT_MUXB[1:0]
OUT_MUXC[1:0]
OUT_MUXD[1:0]
Bits 1:0 - Register CE
Bits 3:2 - Register CE
Bits 5:4 - Register CE
Bits 7:6 - Register CE
00 (binary)
01 (binary)
10 (binary)
11 (binary)
By default, in Component Video output mode, the
CX25870 will transmit:
DAC_A = Video[0] = PR = V
DAC_B = Video[1] = Y
DAC_C = Video[2] = PB = U
DAC_D = Video[3] = Y_DELAY
For EIA-770.1 compliant Component Video out, no other programming steps
are required for the CX25870/871 beyond Table 1-27.
For the more common EIA-770.2-A compliant Component Video out, a few
additional programming steps are required. These are listed in Table 1-28 below:
Table 1-28. Unique Registers Required to Switch CX25870/25871 into EIA-770.2-A- Compliant Component Video Outputs
Register/Bit Name
Location
Value
Comment
SETUP
Bit 1–Register A2
0 (binary)
Required for EIA770.2-A compliance. Removes 7.5 IRE
pedestal normally present within NTSC-M active video
lines.
SYNC_AMP[7:0]
MY[7:0]
Bits 7:0–Register A4
Bits 7:0–Register AC
F0 (hex)
85 (hex)
Multiplication factor for adjusting the analog sync
amplitude tip to –300 mV for EIA-770.2-A.
Additional gain multiplication factor for Y EIA-770.2-A
analog output. This register needs to be increased by
6 percent of its nominal value.
For a NTSC output based on a RGB digital input, this
register would be increased 6 percent to 8C (hex) from a
nominal value of 85 (hex).
100381B
Conexant
1-83
CONEXANT [ CONEXANT SYSTEMS, INC ]
