Canon LBP-1000 Service Manual page 50

CHAPTER 2
2. Operation
Unlike the conventional video interface, which uses an individual signal line for exchanges of
each main signal, the video interface of this printer uses command status.
When sending/receiving status and commands, the engine controller and video controller use
bi-directional STATUS COMMAND signal (SC) and synchronize data with the SERIAL CLOCK
signal (SCLK) output from the video controller.
When the power switch is turned ON, the printer enters the WAIT state.
After the end of the WAIT period, the engine controller sends a ready status to the video con-
troller to notify the video controller that the printer is ready to print.
The video controller sends a print instruction command to the engine controller when the
printer is in the READY state and data of a print page is prepared.
On receiving the print instruction command, the engine controller starts the sequence of the
INITIAL ROTATION. The engine controller starts sending the /BD signal to the video controller
when it detects that the paper has reached the specified position after pick-up operation.
On receiving the /BD signal sent from the engine controller, the video controller sends the
VIDEO signals (/VDO, VDO) synchronized to the /BD signal to the laser driver via the interme-
diate PCB.
The laser driver turns ON/OFF the laser diode based on the /VDO and VDO signals. The
laser beam emitted from the laser diode is scanned across the photosensitive drum surface by
the scanning mirror to form a latent image.
The latent image on the photosensitive drum is transferred onto the paper by the electro-pho-
tographic process and then delivered to the face-down or face-up tray.
While a page is being printed, the engine controller checks if another print instruction com-
mand is being sent from the video controller.
If no command is received, the engine controller completes the PRINT sequence and enters
the LAST ROTATION period. At the end of this period, the printer enters STANDBY mode.
If a print instruction command is being sent, the engine controller continues the PRINT
sequence. After the last rotation operation, the printer enters the STANDBY state.
2 - 16