Print Signal Flow - Canon BJC-55 Service Bulletin

Part 4: Technical Reference

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
Host Computer
BJ Cartridge
Control Board
a
ASIC
e
Figure 4-2 Printing Signal Flow
4-4
DRAM
a
Receive Buffer
b
c
Print Buffer
d
b
Control ROM*
d
: Print Data
: Control Signal
BJC-50