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3: Operation
Colorwriter LSR 2000 Printer
Service Guide
3-21
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The CPU sets the /LSON signal to “H” to complete the initial
APC and then proceeds to the between-pages APC.
Between-pages APC
Immediately after the initial APC, this printer performs the
between-pages APC for pages and colors.
The CPU sets the /VDOENB signal to “H” during the unblanking
period. This causes the laser diode to emit the laser beam at the
intensity set during the initial APC. To ensure that the PDIN signal
is at the specified value, the APCLW signal (8-bit) is changed to
correct the LLCNT signal so as to compensate for the offset from
the target value.
Note:
In order to detect the /BDI signal, the laser diode is turned
ON even during the period that it does not scan the laser beam
across the drum. It is called “unblanking period.”
Horizontal sync control
There is a small fixed mirror (BD mirror) in the optical path of the
laser beam. Upon reaching the scanning start position, the laser
beam is reflected by the BD mirror to the BD PCB in the
laser/scanner unit during the unblanking period.
On receiving the laser beam, the BD PCB generates the beam detect
input signal (/BDI) and then sends it to the gate array in the DC
controller PCB. The gate array produces the horizontal Sync signal
(LSYNC) based on the /BDI signal and then sends it to the video
controller.
Laser diode emission control
The laser driver circuit turns ON/OFF the laser diode in accordance
with the laser drive signal received from the PWM-IC when the
video enable signal (/VDOENB) is “L” and the forcible laser on
signal (/LSON) supplied by the DC controller is “H.”
The gate array (IC109) applies left/right and top/bottom margin
masking to the video signals (/VDO7-/VDO0) in accordance with
the paper size data, and then sends them as Dv2-Dv9 signals to the
PWM-IC in the laser/scanner unit.
The paper size data is supplied to the CPU by the cassette-size
sensing switch for cassette paper feed or by the paper size
specification command issued by the video controller for manual
paper feed.