Samsung sf150t Service Manual page 35

Circuit Description
5-2-7 Operation Panel Control
Communication
The Operation Panel is controlled by the Port 1,
Port2, and Port 5 registers.
Port 1 (E2H) is a 4-bit general output port for LCD
display data.
This port can be configured for normal data (P1.4-
P1.7) or alternately as internal MODEM V.24
interface output signals (P1.0-P1.3).
Port 2 (E4H) is an 8-bit port with both input and
I/O pins.
P2.0-P2.3 are input ports for OPE key scan data,
and P2.6-P2.7 are not used for SF150T.
Port 5 (EAH) is an 8-bit port with both output and
I/O pins.
P5.0 and P5.4 are used for LED control and LCD
enable.
5-2-8 Image Sensor
The shading wave is formed by scanning the white
roller prior to a document.
The slice level is determined by the shading wave,
and compensates for shading distortion according
to the CIS characteristics.
The wave format from the CIS is converted into a 6
bit digital value in the KS16118 image processor,
and processed in B/W or intermediate mode.
CLOCK
SI
SIG
5-4
5-2-9 CIS Input Processor
To process the B/W input signal, maximum (+Vref)
and minimum (-Vref) values of the CIS input signal
are adjusted by calibrating KS16118 in the high state
for maximum level, and setting them to earth for
minimum level.
Shading correction uses a multiplier composed of a
9-bit sequential adder for simple H/W Logic.
5-2-10 CIS Driver
The CIS driver clock (CLK1) frequency is 250 kHz.
A 75% low duty cycle lengthens the charging time.
A start signal (SI) is provided every 10 ms to
match the line scanning time.
Actual image signal (VIN) is provided in less than
6.8 ms, based on A4 paper size using the 250 kHz
clock.
250 KHZ (L:DUTY 75%)
1 LINE
Figure 5-10: CIS Driver Clock Timing
SF150T