Canon BJC 50 Service Manual - Page 92

Part 4: Technical Reference BJC-50 1.3 Print Signal Flow The print signal flow from when the printer receives the print data to when printing is executed is described below. a) The print data (including the control signals) output by the computer is received by the 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 is stored in the DRAM's receive buffer area. b) The print data in the receive buffer is sent to the ASIC and separated into control commands and print data based on the data stored in the control ROM*. The control 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 receives print data stored in the DRAM's print buffer. At the same time, the ASIC receives control commands stored in the control ROM*. e) The ASIC converts the print data into serial data as print drive signals and outputs the serial data to the bubble jet head. In the bubble jet head, the print data is converted from serial signals to parallel print data for each printed line. Printing is executed while the ASIC is controlled by the print control signals. * Control ROM: Flash ROM Control Board Host Computer a a b c d Print Buffer DRAM Receive Buffer ASIC b e BJ Cartridge d Control ROM* : Print Data : Control Signal Figure 4-2 Printing Signal Flow 4-4