Canon BJC-55 Service Manual

1.3 Print Signal FlowThe print signal flow from when the printer receives the print data to when printing isexecuted is described below.a) The print data (including the control signals) output by the computer is received bythe ASIC through the interface, which is controlled by the ASIC on the logic board.Through the dedicated bus between the printer controller and DRAM, print data isstored in the DRAM's receive buffer area.b) The print data in the receive buffer is sent to the ASIC and separated into controlcommands and print data based on the data stored in the control ROM*. Thecontrol commands are processed in the ASIC.c) The print data is stored in the DRAM's print buffer.d) When the ASIC receives the command from the DRAM to start printing, it receivesprint data stored in the DRAM's print buffer. At the same time, the ASIC receivescontrol commands stored in the control ROM*.e) The ASIC converts the print data into serial data as print drive signals and outputsthe serial data to the bubble jet head. In the bubble jet head, the print data isconverted from serial signals to parallel print data for each printed line. Printing isexecuted while the ASIC is controlled by the print control signals.* Control ROM: Flash ROMPart 4: Technical Reference BJC-504-4Host ComputerBJ CartridgeaeControl BoardASICabcdbDRAMReceive BufferPrint BufferControl ROM*: Print Data: Control SignaldFigure 4-2 Printing Signal Flow