hmp8112acn Harris Corporation, hmp8112acn Datasheet - Page 6

• Manufacturer Part Number: hmp8112acn
• Description: Ntsc/pal Video Decoder
• Manufacturer: Harris Corporation

Reset
The RESET pin is used to return the decoder to an
initialization state. This pin should be used after a power-up
to set the part into a known state. The internal registers are
returned to their RESET state and the Serial I
returned to inactive state. The RESET pin is an active low
signal and should be asserted for minimum of 1 CLK cycle.
After a RESET or a software reset has occurred all output
pins are three-stated. The VSYNC, HSYNC, DVLD, ACTIVE
and FIELD output pins must be pulled high to ensure proper
operation. A 10K or smaller pullup resistor to V
recommended.
NTSC/PAL Decoder
The NTSC/PAL decoder is designed to convert incoming
Composite or Separated (SVHS, Y/C) video into it’s YCbCr
component parts. The digital phase locked loops are
designed to synchronize to the various NTSC/PAL stan-
dards. They provide a stable internal 4xf
the Color Sub-Carrier) video clock for color demodulation,
and a line locked clock for vertical spatial pixel alignment.
The decoder uses the CLK to run the A/D converters and the
phase locked loops. This asynchronous master clock for the
decoder eliminates the need for a unique clock source in a
Multimedia application. CLK can run from 20MHz to 30MHz
when using the 16-bit Synchronous Data output Mode. The
user must program the CLK to Color Sub-Carrier Ratio to
match the CLK frequency used (see Internal Phase Locked
Loops discussion). When using the 8-bit Burst Data Output
Mode the CLK should be a 24.54MHz, 27MHz or 29.5MHz
depending on the output video standard chosen. The crystal
oscillator must have a ±50ppm accuracy and a 60/40% duty
cycle symmetry to ensure proper operation. Since the video
data from the external A/D’s are sampled at the CLK fre-
quency a sample rate converter is employed to convert the
data from the CLK rate to the internal decoding frequency of
4xfSC.
7
6
5
4
3
2
1
0
1.6
TEMPERATURE = 25
V
CC
FIGURE 3. CHROMINANCE AMPLIFIER GAIN
1.8
= 5V
2.0
GAIN CONTROL VOLTAGE
2.2
o
C
2.4
2.6
2.8
SC
3.0
(Frequency of
2
C port is
3.2
HMP8112A
CC
3.4
is
4-6
The input sample rate converter will interpolate between
existing CLK samples to create the chroma locked (4xf
samples needed for the color decoder. An interpolation is
done to create the 4xf
applied.
The decoder can be used with the following video sources:
Analog Composite - NTSC M, - PAL B, D, G, H, I, N
And Special Combination PAL N
Analog S - VHS (Y/C) - NTSC M, PAL B, D, G, H, I, N
Color Separation, and Demodulation
To separate the chrominance modulated color information
from the baseband luminance signal, a 2-Line comb filter is
employed. In NTSC signals the color information changes
phase 180
chrominance information at half line intervals throughout the
NTSC video spectrum. Therefore, NTSC has 227.5 cycles of
chrominance per NTSC line. The half of a cycle causes the
next reference burst to be 180
ous line’s burst. The 2-Line comb efficiently removes the
chrominance information from the baseband luminance sig-
nal. When decoding NTSC, the decoder maintains full lumi-
nance bandwidth horizontally throughout the chrominance
carrier frequency range. Unlike most 2 line comb filter sepa-
ration techniques, vertical bandwidth is maintained by
means of a proprietary transform technique.
Reset
The RESET pin is used to return the decoder to an initializa-
tion state. This pin should be used after a power-up to set the
part into a known state. The internal registers are returned to
their RESET state and the Serial I
tive state. The RESET pin is an active low signal and should
be asserted for minimum of 1 CLK cycle. After a RESET or a
software reset has occurred all output pins are three-stated.
The VSYNC, HSYNC, DVLD, ACTIVE and FIELD output pins
must be pulled high to ensure proper operation. A 10K or
smaller pullup resistor to V
FIGURE 4. SAMPLE RATE CONVERSION
o
from one line to the next. This interleaves the
INCOMING VIDEO SAMPLES
4xf
RESAMPLED VIDEO
SC
SC
And Special Combination PAL N
pixel and a correction factor is then
CC
is recommended.
o
out of phase with the previ-
2
C port is returned to inac-
TIME
TIME
SC
)