HMP8112
2
The 2-bit values allow 4 choices of scaling factors. The
sharpness control helps to compensate for losses in the
scaling interpolators that can reduce the amplitude of high
frequency components.
I C Control Interface
2
The HMP8112 utilizes an I C control bus interface to pro-
gram the internal configuration registers. This standard
mode (up to 100 KBPS) interface consists of the bidirec-
tional Serial Data Line (SDA) and the Serial Clock Line
(SCL). The implementation on the HMP8112 is a simple
slave interface that will not respond to general calls and can-
not initiate a transfer. When the device is not active, the SDA
and SCL control pins should be pulled high through external
4kΩ pullup resistors.
TABLE 4. SHARPNESS GAIN FACTOR SELECTS
XF1
0
XF0
0
GAIN FACTOR
SCALED BY 1.0
SCALED BY 2.0
SCALED BY 4.0
SCALED BY 0
0
1
1
0
+5V
+5V +5V
1
1
HMP8112
VIDEO
DECODER
The Color Killer
(AGC Hysteresis and Loop Limits)
4kΩ
4kΩ
41
40
The color killer will disable the color difference path and set
the U and V components to zero. The automatic color killer
circuitry uses the AGC threshold to determine the maximum
and minimum gain factor limits. The loop filter determines
how much the AGC gain factor can be changed within one
line. The maximum gain factor (Max = 8) and the minimum
gain factor (Min = 0.5) will limit the range of the AGC. When
the gain factor exceeds the maximum gain factor of 8, the
gain factor is limited to 8. Once the signal has an amplitude
of 1/16th, the nominal video the color killer is enabled and
the chroma phase locked loop holds it’s last phase refer-
ence. While the color killer is enabled, the U and V compo-
nents are forced to zero. Once the input video signal reaches
1/7th the optimum amplitude the color killer is disabled and
the color is returned.
SDA
SCL
FIGURE 12. PULLUP RESISTOR CONFIGURATION
2
The I C clock/data timing is shown below in Figure 13. The
HMP8112 contains 29 internal registers used to program and
2
configure the Decoder. The I C control port contains a pointer
register that auto-increments through the entire register space
and can be written. The autoincrement pointer will wrap after
the last register has been accessed (Product ID Register) and
should be set to the desired starting address each time an
2
access is started. For a write transfer, the I C device base
address is the first part of a serial transfer. Then the internal
register pointer is loaded. Then a series of registers can be
written. If multiple registers are written, the pointer register will
autoincrement up through the register address space. A stop
cycle is used to end the transfer after the desired number of
registers are programmed.
MAX
GAIN
FACTOR
AGC
GAIN
FACTOR
UV
COLOR
KILLER
÷4096
DATA
MIN
GAIN
2
For a read transfer, the I C device address is the first part of
FACTOR
the serial transfer. Then the internal register pointer is
loaded. At this point another start cycle is initiated to access
the individual registers. Figure 14 shows the programming
flow for read transfer of the internal registers. Multiple regis-
ters can be read and the pointer register will autoincrement
up through the pointer register address space. On the last
data read, an acknowledge should not be issued. A stop
cycle is used to end the transfer after the desired number of
registers are read.
AGC
ENABLE
2
I C
LINE
COUNT
FIGURE 11. LOOP FILTER BLOCK DIAGRAM (HYSTERESIS)
The dynamic range of the AGC allows it to compensate for
video that is 1/8 to 2 times the specified nominal of 1V
.
P-P
Saturation
Product ID Register
The color saturation component is controlled via the Color
Saturation Registers. The color saturation is applied to the
UV components after the AGC function. The saturation value
is multiplied by the UV data to increase the color intensity.
The data range is from 0 to 1.96875 where 1.96875 is the
brightest intensity. This is an 8-bit number in the form:
The HMP8112 contains a product ID register that can be
used to identify the presence of a board during a Plug ’n Play
detection software algorithm. The Product ID code is 12
H
and the register is the last register in the HMP8112 (1B ).
H
Output Data Port Modes
X.XXX XXXX
The HMP8112 can output data in 2 formats, an 8-bit Burst
mode and a 16-bit Synchronous Pixel Transfer mode. In 16-bit
Synchronous Pixel Transfer Mode pixel data is output at the
The default value after a RESET is 1.2074 (9D ).
H
11
HARRIS [ HARRIS CORPORATION ]
