Canon LBP-2000, Service Manual

Page: 65 / 222

CHAPTER 2
2 - 26
b . Video interface signals
Video controller
PCB
DC controller
PCB
J104-
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J5-
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/PPRDY
/CCRT
/SBSY
/PCLK
/STS
/RDY
/TOP
/CBSY
/CCLK
/CMD
/PRNT
/PRFD
/CPRDY
/BDO
/VDO
VDO
Figure 2-2-15
When the power switch is turned on, the Printer enters wait state (WAIT).
When WAIT ends and warm-up rotation ends, the DC controller sends the ready signal (/RDY)
to the video controller, indicaing that the Printer is ready for printing.
The video controller sends the print signal (/PRNT) to the controller when the /RDY signal goes
Low and, in addition, data is ready for printing a single page.
When the /PRNT signal arrives, the DC controller starts the sequence for initial rotation (INTR).
When the sequence for initial rotation ends, the DC controller sends the vertical sync request
signal (/TOP) to the video controller.
In response to the horizontal sync signal (/BDO) from the DC controller, the video controller
sends video signals (/VDO, VDO) synchronized with the /BDO signal and the /TOP signal to the
laser driver by the DC controller.
These video signals (/VDO, VDO) are sent to the laser driver as two low-voltage differential
s i g n a l s .
The laser driver uses these video signals (/VDO, VDO) to turn on or off the laser diode.
The latent image on the photosensitive drum is transferred to paper as part of electrophotograpic
processes, and the output is delivered face-down.
While a single page is being printed, the DC controller checks the presence of /PRNT signal
from the video controller. If not, the Printer stops the print sequence, and starts last rotation
(LSTR), at the end of which it enters standby state (STBY).
If the /PRNT signal is detected, the Printer continues the print sequence until the /PRNT signal
stops, at which time it will execute last rotation and enter standby state.