Canon BJC-55 Series, Service Bulletin

Page: 147 / 249

2) Printer controller section
The printer controller contains the parallel interface controller, print head
controller, scanner head controller, CR motor controller, paper feed motor
controller, buffer controller, DRAM controller, recharge controller, etc. It operate in
synchronization with an external 23.04 MHz external clock input.
Interface controller
The interface controller receives from the computer, 8-bit parallel data which is
synchronized with the data strobe pulse (STROBE) through the BUSY/ACKNLG
handshake. It also controls IrDA and ASK interface signals.
The data received through the interface is stored in the DRAM's receive buffer and
analyzed by the ASIC.
DRAM controller
The DRAM controller is a DRAM-specific bus separate from the MPU section bus.
It controls the 4 M bit DRAM's 10-bit address/16-bit data bus and also executes
read/write control, RAS/CAS control, and refresh control.
Buffer controller
The buffer controller automatically writes the received data to the receive buffer on
the DRAM, manages the receive buffer's remaining capacity, automatically reads
the print buffer, and clears the data after it is read.
Print head controller
The print head controller converts the print data read from the DRAM's print buffer
from parallel to serial and sends the serial data to the print head. For large and
small dot printing, the print head controller outputs 4 heat-enable signals (HENBA,
HENBB, HENBC and HENBD). Each enable signal can be output independently.
Scanner cartridge controller
The scanner cartridge controller tries to operate the printer as a scanner once it
receives a scanner activation message from the host computer. In the scanner
mode, data cannot be removed from the receiver buffer.
Recharge controller
The recharge controller controls the battery recharge controller IC which is driven
by the recharging electrical current, temperature and voltage values transmitted
through the A/D port.
I/O port
The input port contains the home position sensor, the delivery sensor, the paper
end sensor, and a data input signal for the optional ASF unit. The output port
controls the beeper, ERROR LED on/off signals, battery recharge on/off signals,
battery power output on/off signals, A/D port analog switch signal, CR exciter
motor, drive signals and a data output signal for the optional ASF unit.
b) Flash ROM/FONT ROM (IC9/IC10)
This printer has a flash ROM as the control board lacked space for an EPROM. The
4 M-byte flash ROM contains printer control programs and program-rewrite loading
programs. The 8 M-byte FONT ROM contains the bitmap font data for printer
control.
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BJC-50
Part 4: Technical Reference