HMP8170EVAL1 INTERSIL [Intersil Corporation], HMP8170EVAL1 Datasheet - Page 8

• Manufacturer Part Number: HMP8170EVAL1
• Description: NTSC/PAL Video Encoder
• Manufacturer: INTERSIL [Intersil Corporation]

.
Color Subcarrier Generation
The HMP8170 uses a numerically controlled oscillator
(NCO) clocked by CLK2 and a sine look up ROM to
generate the color subcarrier. As shown in Figure 9, the
phase increment value (PHINC) of the NCO may come from
the encoder’s internal look up table, BT.656 ancillary data, or
a control register. The PHINC source is selected in timing
I/O register 2.
-10
-20
-30
-40
-50
-60
-10
-20
-30
-40
-50
-60
0
0
0
0
PAL SQUARE PIXEL
CLK2 = 29.50MHz
NTSC OR PAL
RECTANGULAR PIXEL
CLK2 = 27.00MHz
NTSC SQUARE PIXEL
CLK2 = 24.54MHz
2
FIGURE 7A. FULL SPECTRUM
2
FIGURE 8A. FULL SPECTRUM
4
4
FREQUENCY (MHz)
NTSC OR PAL
RECTANGULAR PIXEL
CLK2 = 27.00MHz
NTSC SQUARE PIXEL
CLK2 = 24.54MHz
FREQUENCY (MHz)
6
8
6
8
FIGURE 8. Cb AND Cr LOWPASS FILTER RESPONSE
PAL SQUARE PIXEL
CLK2 = 29.50MHz
10
8
FIGURE 7. Y LOWPASS FILTER RESPONSE
12
10
14
12
HMP8170
.
INTERNAL
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
FIGURE 9. COLOR SUBCARRIER GENERATION NCO.
BT.656
0
0
0
0
SELECT
I
2
PHINC
C
0.2
NTSC OR PAL
RECTANGULAR PIXEL
CLK2 = 27.00MHz
1
FIGURE 7B. PASS BAND
FIGURE 8B. PASS BAND
PAL SQUARE PIXEL
CLK2 = 29.50MHz
NTSC OR PAL
RECTANGULAR PIXEL
CLK2 = 27.00MHz
NTSC SQUARE PIXEL
CLK2 = 24.54MHz
0.4
NTSC SQUARE PIXEL
CLK2 = 24.54MHz
2
PHINC
NCO RESET
FREQUENCY (MHz)
FREQUENCY (MHz)
0.6
CLK2
3
+
0.8
4
D
1.0
PAL SQUARE PIXEL
CLK2 = 29.50MHz
5
Q
1.2
1.4
6
PHINT
1.6
7