HP 2420 Service Manual - Page 90

Print cartridge memory system The memory tag is a nonvolatile memory built into the print cartridge. The cartridge usage condition is detected as the engine controller reads or writes the data stored on the memory tag. The engine controller renews the information in the prescribed timing and reads or writes it from or to the memory tag. The engine controller commands the memory tag to read or write with the following conditions: ● Read ● Power is ON ● The top cover is closed ● A command has been received from the formatter ● Write ● A page of media is printed. ● A command has been received from the formatter When the engine controller failed to read or write three times in a row, it determines that the memory tag is abnormal and notifies the formatter of a "cartridge memory abnormality warning". Figure 5-15. Print cartridge memory tag 76 Chapter 5 Theory of operation ENWW