hmp8156a Intersil Corporation, hmp8156a Datasheet - Page 12

• Manufacturer Part Number: hmp8156a
• Description: Ntsc/pal Video Encoder
• Manufacturer: Intersil Corporation

BLANK Timing
The encoder uses the HSYNC, VSYNC, FIELD signals to
generate a standard composite video waveform with no
active video (black burst). The signal includes only sync tips,
color burst, and optionally, a 7.5 IRE blanking setup. Based
on the BLANK signal, the encoder adds the pixel and overlay
input data to the video waveform.
The encoder ignores the pixel and overlay input data when
BLANK is asserted. Instead of the input data, the encoder
generates the blanking level. The encoder also ignores the
pixel and overlay inputs when generating closed captioning
data on a specific line, even if BLANK is negated.
FIGURE 13. HSYNC, VSYNC, AND FIELD TIMING FOR
FIGURE 14. HSYNC, VSYNC, AND FIELD TIMING FOR
HSYNC
VSYNC
HSYNC
VSYNC
HSYNC
HSYNC
VSYNC
VSYNC
FIELD
FIELD
FIELD
FIELD
FIGURE 13B. BEGINNING AN EVEN FIELD
FIGURE 14B. BEGINNING AN EVEN FIELD
FIGURE 13A. BEGINNING AN ODD FIELD
FIGURE 14A. BEGINNING AN ODD FIELD
(M, NSM) NTSC AND (M, N) PAL
(B, D, G, H, I, CN) PAL
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HMP8154, HMP8156A
There must be an even number of active and total pixels per
line. In the 8-bit YCbCr modes, the number of active and
total pixels per line must be a multiple of four. Note that if
BLANK is an output, half-line blanking on the output video
cannot be done.
The HMP8154/HMP8156A never adds a 7.5 IRE blanking
setup during the active line time on scan lines 1-21 and 263-
284 for (M, NSM) NTSC, scan lines 523-18 and 260-281 for
(M) PAL, and scan lines 623-22 and 311-335 for (N) PAL,
allowing the generation of video test signals, timecode, and
other information by controlling the pixel inputs appropriately.
Normal Mode Blanking
The relative timing of BLANK, HSYNC, and the output video
depends on the blanking and sync I/O directions. The typical
timing relation is shown in Figure 15. The delays which vary
with operating mode are indicated. The width of the
composite sync tip and the location and duration of the color
burst are fixed based on the video format.
.
When BLANK is an output, the encoder asserts it during the
inactive portions of active scan lines (horizontal blanking)
and for all of each inactive scan line (vertical blanking). The
inactive scan lines blanked each field are determined by the
start_v_blank and end_v_blank registers. The inactive
portion of active scan lines is determined by the
start_h_blank and end_h_blank registers.
The zero count for horizontal blanking is 32 CLK2 cycles
before the 50% point of the composite sync. From this zero
point, the HMP8154/HMP8156A counts every other CLK2
cycle. When the count reaches the value in the
start_h_blank register, the encoder negates BLANK. When
the count reaches the value in the end_h_blank register,
BLANK is asserted. There may be an additional 0-7 CLK2
delays in modes which use CLK.
The data pipeline delay through the HMP8154/HMP8156A is
26 CLK2 cycles. In operating modes which use CLK to gate the
inputs into the encoder, the delay may be an additional 0-7
CLK2 cycles. The delay from BLANK to the start or end of
active video is an additional one-half CLK cycle when the blank
timing select bit is cleared. The active video may also appear to
end early or start late since the HMP8154/HMP8156A controls
the blanking edge rates.
FIGURE 15. HSYNC, BLANK, AND OUTPUT VIDEO TIMING,
COMPOSITE
VIDEO OUT
DATA PIPE
HSYNC
BLANK
DELAY
NORMAL MODE
START H BLANK
SYNC DELAY
November 4, 2005
4343.4