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參數(shù)資料
| 型號： | ADV101* |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | CMOS 80 MHz. Triple 8-Bit Video DAC |
| 中文描述： | 80兆赫的CMOS。三8位視頻DAC |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 187K |
ADV101
–6–
REV. B
T E RMINOLOGY
Blanking Level
T he level separating the
SYNC
portion from the video portion
of the waveform. Usually referred to as the front porch or back
porch. At 0 IRE units, it is the level which will shut off the pic-
ture tube, resulting in the blackest possible picture.
Color Video (RGB)
T his usually refers to the technique of combining the three pri-
mary colors of red, green and blue to produce color pictures
within the usual spectrum. In RGB monitors, three DACs are
required, one for each color.
Sync Signal (
SYNC
)
T he position of the composite video signal which synchronizes
the scanning process.
Gray Scale
T he discrete levels of video signal between reference black and
reference white levels. An 8-bit DAC contains 256 different lev-
els, while a 6-bit DAC contains 64.
Raster Scan
T he most basic method of sweeping a CRT one line at a time to
generate and display images.
Reference Black Level
T he maximum negative polarity amplitude of the video signal.
Reference White Level
T he maximum positive polarity amplitude of the video signal.
Sync Level
T he peak level of the
SYNC
signal.
Video Signal
T hat portion of the composite video signal which varies in gray
scale levels between reference white and reference black. Also re-
ferred to as the picture signal, this is the portion which may be
visually observed.
CIRCUIT DE SCRIPT ION AND OPE RAT ION
T he ADV101 contains three 8-bit D/A converters, with three
input channels, each containing an 8-bit register. Also inte-
grated on board the part is a reference amplifier and CRT con-
trol functions
BLANK
,
SYNC
and REF WHIT E.
Digital Inputs
24-bits of pixel data (color information) R0–R7, G0–G7 and
B0–B7 are latched into the device on the rising edge of each
clock cycle. T his data is presented to the three 8-bit DACs and
is then converted to three analog (RGB) output waveforms.
(See Figure 2.)
T hree other digital control signals are latched to the analog
video outputs in a similar fashion.
BLANK
,
SYNC
and REF
WHIT E are each latched on the rising edge of CLOCK to
maintain synchronization with the pixel data stream.
T he
BLANK
and
SYNC
functions allow for the encoding of
these video synchronization signals onto the RGB video output.
T his is done by adding appropriately weighted current sources
to the analog outputs, as determined by the logic levels on the
BLANK
and
SYNC
digital inputs. Figure 3 shows the analog
output, RGB video waveform of the ADV101. T he influence of
SYNC
and
BLANK
on the analog video waveform is illustrated.
T he REF WHIT E control input drives the RGB video outputs
to the white level. T his function could be used to overlay a cur-
sor or crosshair onto the RGB video output.
T able I details the resultant effect on the analog outputs of
BLANK
,
SYNC
and REF WHIT E.
All these digital inputs are specified to accept T T L logic levels
Clock Input
T he CLOCK input of the ADV101 is typically the pixel clock
rate of the system. It is also known as the dot rate. T he dot rate
and hence the required CLOCK frequency, will be determined
by the on-screen resolution, according to the following equation.
Dot Rate = (Horiz Res)
×
(Vert Res)
×
(Refresh Rate)/
Dot Rate =
(Retrace Factor)
Horiz Res
Vert Res
Refresh Rate
= Number of pixels/line
= Number of lines/frame
= Horizontal Scan Rate. T his is the rate at
which the screen must be refreshed, typi-
cally 60 Hz for a noninterlaced system or
30 Hz for an interlaced system.
= T otal blank time factor. T his takes into ac-
count that the display is blanked for a certain
fraction of the total duration of each frame
(e.g., 0.8).
Retrace Factor
CLOCK
DATA
ANALOG OUTPUTS
(IOR, IOG, IOB, I )
DIGITAL INPUTS
(R0–R7, G0–G7, B0–B7;
SYNC, BLANK,
REFWHITE)
Figure 2. Video Data Input/Output
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| ADV101KN30 | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Analog Devices 功能描述: |
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| ADV101KN80 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ADV101KP30 | 制造商:Rochester Electronics LLC 功能描述:TRIPLE 8 BIT CMOS V.DAC - Bulk 制造商:Analog Devices 功能描述: |
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