lm9831 National Semiconductor Corporation, lm9831 Datasheet - Page 30

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

The state of each pin, True or False (1 or 0), is reflected in the
Status Register.
These are the configurable aspects of these I/O pins:
• Input or Output function. If this bit is set to a 0, the pin is config-
• The polarity of the input. If this bit is set to a 1 (Active High), a
• Level or Edge Sensitive. If this bit is set to 0 (Level Sensitive),
• PAPER SENSE 1 can be programmed to stop the scan (by
• PAPER SENSE 2 can be programmed to stop the scan (by
• If they are configured as outputs, the MISC I/O 1-6 pins can
The default state of the MISC I/O pins is described in detail in the
Register Listing section. The Misc I/O pins revert to their default
states on power-on, after entering USB Suspend, or when the
RESET pin is pulsed high. A soft reset (register 07) does not
reset the MISC I/O pins. The default states of the MISC I/O pins
are:
• MISC I/O 1: Input, edge sensitive, high-to-low transition sets bit
• MISC I/O 2: Input, edge sensitive, high-to-low transition sets bit
• MISC I/O 3: Input, edge sensitive, high-to-low transition sets bit
• MISC I/O 4: Output, voltage on MISC I/O 4 pin = V
• MISC I/O 5: Output, voltage on MISC I/O 5 pin = V
• MISC I/O 6: Output, voltage on MISC I/O 6 pin = 0V.
5.5.1 Adding Function Buttons
Many scanners today feature multiple buttons to select scan,
copy, fax, email, etc. functions. The LM9831’s MISC I/O pins can
be used for these functions. To free up MISC I/O inputs for other
functions, or if more than 6 buttons are required, you can multi-
plex the buttons together. Figure 36 shows how 7 buttons can be
ured as an input. If this bit is set to a 1 the pin is configured as
an output.
high level on that input pin will produce a True reading (1) in the
Status Register. If this bit is set to a 0 (Active Low), a low level
on that input pin will produce a True reading (1) in the Status
Register.
the Status Register will reflect the current state at that sensor
input pin. If this bit is set to 1 (Edge Sensitive), the Status Reg-
ister for that input will be True (1) if there were any False to
True transitions at that sensor input pin since the last time the
Status Register was read. Reading the status register clears
the state of all the edge sensitive inputs to False (0).
clearing the Scanning bit) when its state (as reflected in the Sta-
tus Register) changes from False to True. This is useful in flat-
beds to prevent the motor from trying to step past the limits of
travel of the system. In sheetfed systems, PAPER SENSE 1
can be used to detect whether or not the user has inserted a
document to be scanned.
clearing the Scanning bit) and set its bit in the Status Register
to True a programmable number of lines after its input pin
changes state from False to True. In sheetfed scanners this is
useful if the PAPER SENSE is located before the scanner array,
where the sensor will change states before all of the paper has
been scanned. For flatbed scanners this sensor can be used to
detect the home position.
have their outputs set to +5V or 0V by writing a 1 or a 0 to the
appropriate bit.
2 of register 2.
3 of register 2.
4 of register 2.
D
D
.
.
30
multiplexed into only 3 MISC I/O lines. Figure 37 shows how to
decode the data in register 2 to determine which button was
pressed. This multiplexing technique can easily be scaled to
allow for more or less buttons with the minimum number of MISC
I/O lines.
.
5.6 The Brains
This is the master control section that keeps track of the position
of the CCD pixel going through the analog front end, the color of
that line of CCDs (for single output CCD illumination control), the
stepper motor, and all other system coordination.
6.0 Communicating with the LM9831
Everything on the LM9831 (configuration settings, image data,
coefficient data, and gamma tables) is accessed through the
Configuration Register. Configuration Register I/O is done
through two steps. The first step is to write the address (0 through
7F) of the configuration register to be read from or written to. The
second access is the data operation (a read or a write) for that
address. The address only needs to be written once. After an
address is written, any number of reads and/or writes may be
made to that address.
Registers 0, 1, and 2 are read-only registers. Writing to these
addresses may affect various counters inside the LM9831 and
should therefore be avoided. Bits 4 of register 3 is also read only,
however it is OK to write to register 3. All of the remaining config-
uration registers can be read from and written to using this proto-
col.
6.1 The DataPort: Reading and Writing to Gamma, Offset,
and Gain Memory
Because the gamma table and the shading and offset correction
blocks of RAM are very large, the LM9831 uses an indexed
A
Figure 37: Truth Table for Remote Wakeup With Up To
Figure 36: Remote Wakeup With Up To 7 Switches
Switch
C
D
G
A
B
E
F
B
MISC I/O 1
C
0
0
0
1
0
1
1
7 Switches
D
22k 22k 22k
MISC I/O 2
E
0
0
1
0
1
0
1
F
G
+5V
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MISC I/O 3
MISC I/O 1
MISC I/O 2
MISC I/O 3
0
1
0
0
1
1
0