LM9830VJDX NSC [National Semiconductor], LM9830VJDX Datasheet - Page 32

• Manufacturer Part Number: LM9830VJDX
• Description: LM9830 36-Bit Color Document Scanner
• Manufacturer: NSC [National Semiconductor]

scan).
To improve the performance of this mode, there is also a 12 bit/8
slot (full duplex) mode available. In this mode coefficient reads
take 1 MCLK each (a total of 2 MCLKs). The high and low bytes
of the 12 bit word are each read from RAM and transmitted to the
host in 1 MCLK cycle. To slightly reduce the speed requirements
of SRAM, the high and low byte writes to RAM are given 2
MCLKs each. This allows the host to read pixel data from the
SRAM while scanning, dramatically reducing the time required to
scan versus using the half duplex mode.
To minimize EMI and on-chip noise, the SRAM output drivers (A0-
A17, DB0-DB7, and RD and WR) have four output current set-
tings, 0-3. The output current level is set by bits 2 and 3 of Config-
uration Register 43.
4.5 Misc. I/O
These four pins are used for paper sensing, LED displays, user
start buttons, etc.
Two pins are dedicated inputs: Paper Sensor #1 and Paper Sen-
sor #2. The other two pins, Misc I/O #1 and Misc I/O #2, can be
configured as inputs or outputs.
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:
• 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),
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
Coefficients
Coefficients
128K SRAM, 600 DPI
64K SRAM, 300 DPI
Line Buffer
Line Buffer
Figure 43: Typical Memory Maps for External SRAM
Current
Setting
0
1
2
3
16384
49152
32768
98304
(mA)
I
3.5
12
21
OL
6
(mA)
-7.5
I
-17
-32
OH
-4
Coefficients
256K SRAM, 600 DPI
Line Buffer
t
20pF
F
29
17
(ns)
8
5
229,376
32768
t
R
20pF
25
13
(ns)
6
3
32
• Paper Sensor #1 can be programmed to stop the scan (by
• Paper Sensor #2 can be programmed to stop the scan (by
• The Misc I/O 1 and Misc I/O 2 pins can have their outputs set to
4.6 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.
5.0 Communicating with the LM9830
Everything on the LM9830 (configuration registers, 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 LM9830 and
should therefore be avoided. All of the remaining configuration
registers can be read from and written to using this protocol.
5.1 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 LM9830 uses an indexed
method of reading and writing them, called the DataPort. Four
addresses in the Configuration Register are used to implement
this mode, as shown in Figure 44.
of all the edge sensitive inputs to False (0).
clearing the Scanning bit) when its state (as reflected in the
Status Register) changes from False to True. This is useful in
flatbeds to prevent the motor from trying to step past the limits
of travel of the system. In sheetfed systems, Paper Sensor #1
can be used to detect whether or not the user has inserted a
document to be scanned.
clearing the Scanning bit) and change its bit in the Status Reg-
ister 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 sensor 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.
+5V or 0V by writing a 1 or a 0 to the appropriate register.
Configuration
Register
Address
3
4
Figure 44: DataPort
DataPort
DataPort
Address
Target/
Name
(MSB)
Color
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b12 - b8
b3- b0
Bits