HP Color LaserJet Enterprise CP5525 Service Manual - Page 60

Memory tag The memory tag is a non-volatile memory chip in the cartridge that stores information about usage for the cartridge. The product reads and writes the data in the memory tag. The DC controller determines a memory tag error and notifies the formatter when it fails to either read from or write to the memory tag. Cartridge presence detection The DC controller detects the presence of the cartridges by monitoring the cartridge e-label and ground circuit. When the DC controller determines a cartridge absence, it notifies the formatter. Toner level detection The DC controller detects the remaining toner level in a cartridge by the optical detection method. The DC controller notifies the formatter of the remaining toner level. Cartridge life detection The DC controller detects the cartridge life by monitoring the total operational wear limit or remaining toner level of the cartridge. The DC controller determines a cartridge end of life and notifies the formatter when the operational wear limit of the cartridge reaches a specified amount or the cartridge runs out of toner. Developing unit engagement and disengagement control The developing unit engagement and disengagement control engages the developing unit with the photosensitive drum or disengages the developing unit from the drum depending on the print mode: fullcolor mode or black-only mode. The developing unit is engaged only when required, preventing a deterioration of the drums and maximizing their life. The developing disengagement motor rotates the developing disengagement cam. As the cam rotates, the developing unit engages with or separates from the photosensitive drum. When the product is turned on and when each print job is completed, all four of the developing units disengage from the photosensitive drums. When the print mode is in full-color mode, all of the developing units engage with the drums. When the print mode is in black-only mode, only black developing unit engages with the drum. 36 Chapter 1 Theory of operation ENWW