Closed-Caption Decoder
Functional Description
Panasonic Semiconductor Development Company MN102H75K/F75K/85K/F85K LSI User Manual
228
Panasonic
9.3 Functional Description

9.3.1 Analog-to-Digital Converter

The constants shown in figures 9-2 to 9-4 are recommended values only. Operation at these values is not guaranteed.

The analog-to-digital converter (ADC) converts the clamped video signal to 8-bit

digital data using a 12-MHz sampling clock. Figure 9-2 shows an example con-

figuration using the recommended external pin connections. In this example, both

caption decoders are used. Figure 9-3 shows the recommended connection when

neither decoder is used, and figure 9-4 shows that when only CCD0 is used.

Figure 9-2 Recommended ADC Configuration
Figure 9-3 External Connection with
Both CCD0 and CCD1 Unused Figure 9-4 External Connection with
Only CCD1 Unused
+
+
560 pF
240
A/D
VREFH
VREFL
CVBS0
CVBS1
CLL
CLH
VREFHS
VREFLS
IN
OUT
CLK
Power Down
ADDATA[7: 0]
A/D
VREFH
VREFL
IN
OUT
CLK
Power Down
ADDATA[7: 0]
+
+
1 µF
1 µF
1 µF
1 µF
+
+
Clampingcircuit
560 pF
240
ADC0ON
(PCNT0: x’00FF90’, bit 4)
VBI0OFF
(PCNT0: x’00FF90’, bit 0)
3.3 V
3.3 V
3.3 V
6.8 k
8.2 k
33 k
18 k
1 k
1 k
1µF
1 µF
3.3 V
3.3 V
8.2 k
18 k
VIDEO IN 0
VIDEO IN 1
Low pass filterLow pass filter
fSYSCLK
(12 MHz)
ADC1ON
(PCNT0: x’00FF90’, bit 5)
VBI1OFF
(PCNT0: x’00FF90’, bit 1)
1k
VREFHS
CVBS0
(Used as P31)
CVBS1
(Used as P32)
VREFLS
CLH
(Used as P30)
CLL
(Used as P33)+VIDEO IN1 µFVREFHSCVBS0CVBS1(Used as P32)VREFLSExternalcircuit33 k6.8 kCLLCLH