MN86157 Datasheet, PDF (3/8 Pages) Panasonic Semiconductor – Shading Correction LSI

For Communications Equipment
MN86157 Block Configuration
The MN86157 consists of four basic blocks: (1) A/D
converter, (2) distortion coefficient mapping ROM, (3)
multiplier, and (4) controller.
The following are brief descriptions of each block.
(1) A/D converter
This uses comparison with the reference voltages
to convert the scanner's image data signal from
the VIN pin to a 7-bit digital output.
(2) Distortion coefficient mapping ROM
This constitutes a look-up table for converting the
A/D converter output to a final value for storage
in the external RAM.
(3) Multiplier
This provides high-speed parallel multiplication
of 7 × 7 bits data.
(4) Controller
This controls operation of the shading correction
circuits, the A/D converter, and interface to
external ROM or RAM.
MN86157
Operation
Shading correction (MODE pin at "H" level)
• Fixed distortion coefficients (external memory
is ROM)
This configuration provides 6-bit corrected data
using fixed distortion coefficients stored in an
external ROM and thus invariant.
• Adaptive distortion coefficients (external
memory is RAM)
This configuration provides 6-bit corrected data
using distortion coefficients, stored in external
RAM, that the chip constantly updates using
white reference plane line training.
• Pixels per line
The chip supports line lengths up to 4096 pixels
with a built-in 12-bit address counter supporting
interfaces to two 2¹¹ × 8-bit RAM chips or the
equivalent of a 2732 ROM (2¹² × 8 bits).
• Input clock
The chip uses an input clock signal with a
frequency twice that of the image clock.
• Selecting correction range
The ROS pin provides a choice of two correction
ranges and consequently correction precisions.
ROS
H
L
Correction
Range
50%
75%
Correction
Precision
±1.5%
±3.0%
• Correction start/stop function
Pulling the INHI pin to "L" level in the middle
of a line suspends correction and maintains the
output data at its current value. Returning the
pin to "H" level restarts correction.
• Auto clamp and overflow functions for output
data
If the image input signal level exceeds the white
reference plane level, the chip clamps the output
data at the full-scale value (3F_H) and drives the
overflow pin (OVF) at "H" level.