Canon LBP-1210 Service Manual page 110

CHAPTER 2
C. Operation
Unlike the conventional video interfaces, which use a specified signal line for each signal, the
video interface of this printer uses command status.
When the power is turned ON, the printer enters a wait (WAIT) state. After this state, the
engine controller sends a ready status that indicates the printer is ready to print. In response
to this status, the interface controller sends a print command to the engine controller.
Upon reception of the print command, the engine controller starts the initial rotation (INTR)
sequence. When the engine controller detects that print paper has been picked up and has
reached the specified position, it starts sending the /BD signal to the interface controller.
With the receipt of the /BD signal, the interface controller sends the VIDEO (/VDO, VDO) sig-
nals synchronized with the /BD signal to the laser driver through the intermediate PCB, where-
as the engine controller generates the LASER CONTROL (CNT0, CNT1) signals and sends them.
Based on these video signals, the laser driver turns ON and OFF the laser diodes. The laser
beam, emitted from the laser diode, hits the four-sided mirror and scans across the photosen-
sitive drum surface, forming a latent image.
The latent image on the photosensitive drum is then transferred onto paper by electrophoto-
graphic process, and finally paper is delivered to the face-down or face-up tray.
While printing one page, the engine controller checks if another print command is being sent
from the interface controller. If no command is received, the printer completes the print (PRNT)
sequence and enters the last rotation (LSTR) period. At the end of this period, the printer enters
the standby (STBY) state. Conversely, if a print command is being sent, the printer continues
the print sequence. The printer then performs a last rotation operation and enters the standby
state.
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