lm9831 National Semiconductor Corporation, lm9831 Datasheet - Page 28

• Manufacturer Part Number: lm9831
• Description: 42-bit Color, 1200dpi Usb Image Scanner
• Manufacturer: National Semiconductor Corporation

• There is a bit for Fake Optical Black Pixels (register 19, bit 2).
5.3 AFE Operation
The LM9831 supports the following operation modes, controlled
by registers 26 and 27:
• 3 Channel Pixel Rate Mode. In this mode all three channels are
• 3 Channel Line Rate Mode. In this mode all three channels are
the CCD/CIS, except when it is in Reset or Standby (Register 7
bit 2 or 3 = 1).
This is used with Dyna CIS sensors. In this mode, the RS out-
put pulses once inside the TR1 pulse, then is held high until the
end of the optical black pixels. The TR1 pulse is extended until
the trailing edge of the first RS pulse. This mode works for TR1
only, under all TR1 settings (normal and CIS TR1 Timing
modes 1 and 2).
converted with the multiplexer in front of the ADC switching at
the ADC conversion rate, producing interleaved RGB data that
is transferred to RAM. The ADC runs at MCLK/8, each chan-
nel’s pixel rate is MCLK/24. Each color has its own offset and
gain coefficients. This mode typically uses Illumination Mode 1.
converted with the multiplexer in front of the ADC switching at
the line rate, producing a line of Red data, followed by a line of
Green data, followed by a line of Blue data, etc. that is trans-
ferred to RAM. The selected channel and the ADC both run at
MCLK/8. Each color has its own offset and gain coefficients.
This mode typically uses Illumination Mode 1.
TR1
RS
C
C
D
ADC Out LIne 1: RGBRGBRGBRGBRGB...
ADC Out LIne 2: RGBRGBRGBRGBRGB...
ADC Out LIne 3: RGBRGBRGBRGBRGB...
ADC Out LIne 4: RGBRGBRGBRGBRGB...
Trailing edge of
Figure 28: 3 Channel Pixel Rate Mode
first RS pulse
Figure 27: Fake Optical Black Pixels
Green Channel
Blue Channel
Red Channel
Pixel-Rate
Multiplexing
End of Optical
ADC
Black Pixels
28
In the 3 Channel Line Rate Mode three TR pulses are generated.
TR
TR
color can be “skipped”, increasing the integration time for that
color. In the example shown in Figure 30, the red channel sees 2
times the integration time of the green channel, and the blue
channel sees 3 times the integration time of the green channel.
Each channel can be independently programmed to drop 0, 1, or
2 TR pulses.
Each color’s TR pulse can be programmed to occur in position 1
(inside Ø1 high) or position 2 (inside Ø1 low), as shown in Figure
31.
• 1 Channel Grayscale: Uses the selected channel’s offset and
TR
TR
TR
Multiplexer
Channel
TR
TR
TR
gain coefficients for all lines. 1 Channel Grayscale is used to
scan a grayscale images. This mode typically uses Illumination
Mode 1 when used with a 3 Channel Color sensor, or Illumina-
tion Mode 3 when used with a 1 Channel sensor.
RED
BLUE
Ø1
RED
GREEN
BLUE
RED
GREEN
BLUE
Figure 30: 3 Channel Line Rate TR Pulse Timing
Figure 31: 3 Channel Line Rate Mode with 2 TR
is the TR1 output, TR
C
C
D
is the CP2 output. In this mode TR pulses for a particular
ADC Out LIne 1: RRRRRRRRRRRRRRR...
ADC Out LIne 2: GGGGGGGGGGGGGG...
ADC Out LIne 3: BBBBBBBBBBBBBBBBB...
ADC Out LIne 4: RRRRRRRRRRRRRRR...
Figure 29: 3 Channel Line Rate Mode
t
INT (RED)
Green Channel
1
Blue Channel
Red Channel
Red
2
Pulse Positions
Green
t
INT (GREEN)
GREEN
Blue
1
t
is the TR2 output, and
INT (BLUE)
Line-Rate
Multiplexing
Red
ADC
2
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Green