ML6440
FUNCTIONAL DESCRIPTION (Continued)
internal data register low (D[7:0]=0) which defaults to
automatic combing of NTSC/CCIR601 composite video.
The RST pin resets the comb logic including the internal
data register on active low but does not clear the line
delays. This part requires a timed reset pulse. On power
up or at any time a return to automatic combing of NTSC/
CCIR601 composite video is required the reset pin must
have been high for at least 5 micro seconds. Then taken
low for at least one micro second before returning high
again to resume normal operation. Neither pulse width
nor rise and fall times are critical.
The Y+C/CV selection bit, D7, controls whether Y+C or CV
format is the source for the comb filter. Setting this bit low
selects the composite input pins, which is combed by
default. Setting the bit high selects the Y+C inputs as the
source for video (see bypass section). This source is not
combed and the Y+C inputs are not activated until the S/P
pin is rising-edge triggered.
In most applications a microprocessor will be available to
provide timing and control waveforms. It will provide this
reset pulse and if needed set the appropriate comb filter
mode. In non processor systems an R C network can
provide this reset pulse. See Figure 5.
Adaption thresholds 2 through 0 are D6 through D4,
respectively. These set the adaption behavior from
automatic (D[6:4]=000) to one of seven settings ranging
from fine tuning of computer graphics to photographic
images. See Table 4.
CHROMA AND LUMA BYPASS OPERATION
Comb modes 1 and 0, (D3 and D2, respectively) are used
to enable and disable adaption separately on Y and C
data. For NTSC, if D[3:2]=<00>, then Y is adaptive and C
is always combed. For NTSC, if D[3:2]=<01>, both Y and
C are adaptive. For PAL, if D[3:2]=<00>, then both Y and
C are adaptive. For PAL, if D[3:2]=<01>, then Y is
adaptive and C is combed. For NTSC and PAL, if
D[3:2]=<10>, then Y and C are forced to comb mode. For
NTSC and PAL, if D[3:2]=<11>, then both Y and C are in
bandsplit filtering mode only. See Table 5.
This mode can be activated by setting the internal bit
D7 = 1 either through the serial or parallel programming
modes. Once the register is set (D7 = 1), the comb filter
will look at the inputs for luma on the CV[7:0] pins for a
luma bypass to the outputs of the Y[7:0] pins respectively;
as well as inputs for chroma on the CI/DI[7:0] pins for a
chroma bypass to the outputs of the C[7:0] pins
respectively. The comb filter will continue to look at the
inputs as long as D7 is set high.
The D1 bit sets the choice of data rates between CCIR601
and Square pixel. CCIR601 is active low. Square pixel is
active high. The last bit, D0, select the standard, NTSC or
PAL. NTSC is active low. PAL is active high. See Table 2.
Data presented to the inputs (CI/DI[7:0]) is not interrupted
in the color processing path when S/P is held high or low.
Therefore, it is recommended that S/P activity be limited to
sync or blanking intervals in the video to avoid unwanted
visual artifacts during register programming.
The remaining pin function controls are independent of
the data register: CLK, RST, and OE. The CLK pin requires
a clock at the rates listed in Table 2. Its duty cycle must
meet the duration minimum for high and low.
Clock Timing
Figure 6 depicts digital video input and output timing for
valid data.
60%
40%
13.5MHz CLOCK
20ns
Y/C OUTPUT
CV INPUT
Y OR C DATA
15ns
Y OR C DATA
0ns
CV DATA
CV DATA
Figure 6: Clock Timing
11
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
