3: Operation
Colorwriter LSR 2000 Printer
Service Guide
3-17
When the scanning mirror rotates at a constant speed, the laser
beam scans at an even speed across the photosensitive drum. A
latent image is formed on the photosensitive drum as it also is
rotating at a steady speed.
Video data processing
The video data supplied by the video controller is comprised of 8-
bit video signals (/VDO0-/VDO7) for each of the four colors: M
(Magenta), C (Cyan), Y (Yellow), and Bk (Black), and the image
mode select signal (/IMCHR) used to set either the text mode
(binary mode) or the image mode (half-tone mode). See Figure 3-9
on page 3-18.
In the image data of the Colorwriter there is both full-color mode
and mono-color mode. In the full-color mode, the video controller
sends the video signals in the order of M, C, Y, and Bk to the DC
controller. In the mono-color mode, it only sends the video signals
for a single color.
The video signals (/VDO0-/VDO7) and the /IMCHR signal sent
to the DC controller by the video controller are sent to the gate
array (IC109) via IC111 (line memory). IC109 processes /VDO0-
/VDO7 to perform the image masking (see Figure 3-11 on
page 3-22), half-tone correction (see Figure 3-9 on page 3-18).
Subsequently, they are converted to 8-bit video data signals (Dv2-
Dv9) and mode setting signals (M1-M8) in IC109 and then sent to
the PWM PCB in the laser/scanner unit. The Dv2-Dv9 signals are
video data signals containing halftone information. The M1-M8
signals control the image mode selection.
The PWM circuit modulates the Dv2-Dv9 signals into PWM
signals and sends them as laser drive signals to the laser driver PCB.
