The memory data that the memory controller sends also contains the status of any error that has
occurred during the read/write operation. When the error status is sent, the DC controller PCA makes
up to four attempts to read the operation. If the error is not cleared after the operation, the DC
controller PCA determines one of the following error conditions: sub-CPU failure, memory-data
abnormality, or memory-access abnormality.
CAUTION Removing the print cartridge when the top cover interlock is overridden disables
the cartridge memory.
Image-formation process
The image-formation process is divided into stages.
Figure 4-12 Stages of image-formation
1. Primary charge (conditioning)—The primary-charging roller in the print cartridge applies a
uniform negative charge to the surface of the drum. The primary-charging roller is made of
conductive rubber. An AC bias is applied to the roller to erase any residual charges from any
previous image. A negative DC bias is applied by the charging roller to create a uniform
negative potential on the drum surface.
2. Laser-beam exposure (writing)—Two laser diodes project laser beams onto a rotating
scanning mirror. As the mirror rotates, the beams reflect off of the mirror, first through a set of
focusing lenses, then off a mirror, and finally through a slot in the top of the toner cartridge, and
onto the photosensitive drum. The twin beams sweep the drum from left to right, discharging the
negative potential wherever the beams strike the surface. This creates a latent electrostatic
image, which later is developed into a visible image.
3. Developing—At this stage of the process, the latent electrostatic image is present on the drum.
The toner particles obtain a negative surface charge by rubbing against the developing cylinder,
which is connected to a negative DC supply. The negatively charged toner is attracted to the
discharged (exposed, grounded) areas of the drum, and is repelled from the negatively charged
(unexposed) areas.
4. Transfer—During the transfer process, the toner image on the drum surface is transferred to
the paper. The transfer charging roller applies a positive charge to the back of the paper and
causes the negatively charged toner on the drum surface to be attracted to the paper. After
separation, the drum is cleaned and conditioned for the next image.
ENWW Image-formation system 133
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