Canon CLBP-460PS, Service Manual

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b. Drum cartridge memory
The drum cartridge memory (EEPROM) has a read area and a read/write area. The read area is
exclusively for reading and stores the identification code for the drum cartridge and threshold
value for the drum cartridge life. The DC controller reads data from or writes data into the
read/write area at the specified timing to check the drum cartridge life and waste toner full.
The data stored in the drum cartridge memory is transferred to the register in the D-CPU on
the DC controller at the following timings. Based on this data, the D-CPU writes the updated
data into the drum cartridge memory.
The timings for reading from and writing into the drum cartridge memory are as follows:
Read timing
• When the power is turned ON
• When the drum cartridge drawer is closed
Write timing
• When the power is turned OFF
• When the drum cartridge drawer is opened
• Whenever 20 sheets are delivered (or after continuous printing ends or if a jam occurs)
The printer checks for a drum cartridge memory error during reading or writing.
If writing or reading fails three times continuously (the check sum is not correct), the DC con-
troller notifies the video controller of the abnormal drum cartridge memory.
Figure 2-4-4
c. Photosensitive drum life detection
The DC controller detects whether the end of the drum life has been reached or not based on
the data stored in the drum cartridge memory.
The photosensitive drum consumption time data sent from the DC controller is written into
the drum cartridge memory. The DC controller updates the drum consumption time at the spec-
ified timing. When the accumulated drum consumption time reaches the specified value, the
DC controller determines that the end of the drum life has been reached and notifies the video
controller of the drum life warning.
This printer is capable of printing after the drum life warning has been reported. After the
warning, the DC controller continues to update the drum consumption time data in the drum
cartridge memory. When the accumulated drum consumption time reaches the specified value,
the DC controller assesses that the limit of the drum life has been reached, stops the printer,
and reports it to the video controller.
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CHAPTER 2
DC controller PCB
Drum cartridge
Drum cartridge memory
D-CPU
Drum cartridge memory data