26
0
( )
( )
n
n
H z
h n z
−
=
=
∑
Internal Modules
126
SPRUHI7A – December 2012 – Revised June 2016
Copyright © 2012–2016, Texas Instruments Incorporated
High-Definition Video Processing Subsystem (HDVPSS)
1.2.6.2.14 DAC Output
1.2.6.2.14.1 DAC Output Level
The VENC has one channel 12-bit digital outputs for DAC input. The DAC output code can be optionally
inverted by the DAIV register.
1.2.6.2.14.2 DAC Output Configuration
It is your choice to specify which DAC outputs which video signal. DA0S-DA1S registers specify the DAC
output signal as shown in
.
Table 1-42. DAC Output Select
DAxS
DAC Output
0
CVBS
-15
Reserved
1.2.6.2.14.3 DAC Oversampling
The VENC is capable of 2x oversampling for the final DAC output. The 2x DAC oversampling eases the
external analog filter cost as it can eliminate the unwanted image around the sampling frequency of clk2x.
Setting DAUPS enables 2x oversampling. The oversampling filter is comprised of a 27 tap symmetric FIR
filter with the programmable coefficients. The transfer function is expressed as:
The clk4x is used in the oversampler as a DAC sampling clock. Its frequency should be double of clk2x if
the hardware is configured to support 2x oversampling. Otherwise, the clk4x should be identical to clk2x.
Whether or not to support 2x oversampling can be configured by INC_DUPS parameter in the Verilog
HDL.
Table 1-43. DAC 2x Oversampling Filter Coefficients
Coefficients
Value
Default
h(0), h(26)
DUPFC0
0
h(1), h(25)
0
0
h(2), h(24)
DUPFC1
0
h(3), h(23)
0
0
h(4), h(22)
DUPFC2
0
h(5), h(21)
0
0
h(6), h(20)
DUPFC3
0
h(7), h(19)
0
0
h(8), h(18)
DUPFC4
6/128
h(9), h(17)
0
0
h(10), h(16)
DUPFC5
-20/128
h(11), h(15)
0
0
h(12), h(14)
DUPFC6
78/128
h(13)
1
1