Canon MultiPASS C50, Service Manual

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a) MPU (IC1)
Printer controller (IC5) is controlled by the Control/CG ROM (IC3) program to control printer mode
operations.
b) Control/CG ROM (IC3)
Besides the printer hardware control program and font image data, the following data are stored in the
Control/CG ROM.
• Emulation software
This is the control program for the printer, which can emulate either IBM Proprinter X24E, or EPSON
LQ-2550.
• Font image data
The 360 dpi character design data for each of the BJ cartridge nozzles.
When the printer is emulating IBM Proprinter X24E, the character designs from Character Set 1, 2,
All Characters Chart, Code Page; 437(USA)/ 850 (Multilingual)/ 852 (East Europe)/ 855 (Cyrillic)/
857 (Turkish)/ 860 (Portuguese)/ 863 (Canadian French)/ 864 (Arabic)/ 865 (Norway)/ 869 (Greek)
can be selected. When the printer is emulating EPSON LQ-2550, the EPSON Italics Character Set,
EPSON Graphics Set can be selected, and the language chosen from the International Character Set.
• Mask patterns in fine mode
c) Printer controller (IC5)
The main functions of the system controller as follows:
• Interface controller
The centronics interface controller receives 8-bit parallel data sent from the computer in
synchronization with the data strobe pulse by BUSY / -ACK handshaking It controls other interface
signals. The data received from the interface are stored in the receive buffer in DRAM, and is
analyzed by the MPU. If the printer initialize signal -INIT is input to the printer controller and MPU
from the interface, the printer controller outputs the BUSY status immediately, and the MPU prints
printing data stored in the print buffer, then initializes the printer.
• Buffer controller
The buffer controller automatically writes received data into the receive buffer in DRAM, controls the
remaining data in the receive buffer, reads data from the receive buffer, and clears data after reading.
d) DRAM (IC4)
Besides the printer hardware control data storage area, the DRAM comprises the following;
• Input buffer
Reception data from the interface are stored momentarily. The data are then analyzed by the MPU,
and then erased to make room for the next data.
• Printer buffer
Two lines of BJ cartridge print data are stored. After being printed out, the data are then erased to
make room for the next data.
• Download buffer
When emulating the IBM Proprinter X24E, besides the data stored in the ROM, font image data are
transferred from the computer and stored.
Part 2: Printer
2-6