User manual

95.08.23.11.29
Color LaserWriter 12/600 PS Basics & Theory 1–33
Video Data
Processing
The video data supplied by the I/O controller is composed of 8-bit
video signals (
VDO0-VDO7) for each of four colors, M (Magenta), C
(Cyan), Y (Yellow), and K (Black), and the Image Mode Select signal
(
IMCHR) which is used to set either the text mode (binary mode) or the
image mode (halftone mode).
Note: In order to ensure that text and halftone images are each properly
printed out, the printer switches its image mode via the
IMCHR signal
sent by the I/O controller.
In the image data of the printer there is both full-color mode and mono-
chrome mode. In the full-color mode, the I/O controller sends the
video signals in the order of M, C, Y, and K to the DC controller. In the
monochrome mode, it sends the video signals for only a single color.
The video signals (
VDO0-VDO7) and the IMCHR signal sent to the DC
controller by the I/O controller are sent to the gate array (IC109) via
IC111 (line memory). IC109 processes
VDO0-VDO7 to perform the
image masking, halftone correction, etc.
Note: The printer incorporates the halftone correction table in the DC
controller so that the ideal halftone image can be obtained. This allows
the video signals (
VDO0-VDO7) sent by the I/O controller to be
corrected and converted to the video data signals (
DV2-DV9). They are
subsequently output to the laser driver.
The signals are then converted to 8-bit video data signals (
DV2-DV9)
and mode setting signals (
M1-M8) in IC109 and then sent to the PWM
board in the laser/scanner assembly. The
DV2-DV9 signals are video
data signals containing halftone information. The
M1-M8 signals
control the image mode selection, etc. The PWM circuit modulates the
DV2-DV9 signals into PWM signals and sends them as laser drive
signals to the laser driver board.
The printer includes an anti-counterfeiting function whereby a pattern
unique to the printer is invisibly marked on every printout.
Line
Memory
IC109
IC111
M 1 to 8
Dv2 to 9
IC403
PWM-IC
Laser Driver BoardDC Controller Board
Image
Masking
Halftone
Correction
VDO 0-7
IMCHR
Laser
Drive
Signal
Laser
Driver Circuit