Canon LBP-1260, Service Manual

Page: 49 / 218

diode control
Laser emission is controlled by
VIDEO signal which is sent from
the video controller and processes the
paper size data.
The paper size data is input to the CPU
from the cassette size sensing switches for
cassette feed and by the paper size
command from the video controller for
multi-purpose tray feed.
The CPU transfers the
signal from the video controller to the laser
driver as it is as the signal
The CPU sends data to the gate array
to generate the IMAGE TOP ERASE
AND BOTTOM ERASE signal and
H O R I Z O N T A L M A S K s i g n a l ( M S K )
according to the paper size data from
and MSK are used by
and not output externally.)
To prevent the laser beam from writing
on the non-Image area during the
unblinking period,
makes the
DATA ENABLE signal “L”
only when the TOPE and MSK signals are
“L”. The laser driver switches the laser ON
when the
signal is and the
signal is “L”.
The gate array generates the
UNBLINKING according to the
BD INPUT sent from the BD
PCB in the laser/scanner unit. sets
the UBL signal to d u r i n g t h e
unblinking period and sets the FORCIBLE
LASER ON
The laser driver
switches the laser diode ON when the
is
Figure
2-13
Notes: 1. Indicates the area where the
laser beam writes on the drum.
2. The duration of T2 vary
according to paper size. The
duration of
becomes the
legal size time when the printer
does not recognize the width of
the paper (maximum printable
width). It is the paper size
c o m m a n d f r o m t h e v i d e o
controller has not specified it on
the multi-purpose tray paper
feeding.
The TOPE signal becomes
after the prescribed time of the
multi-purpose tray paper end
sensor becomes OFF.
2-12