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Part 4: Technical Reference
BJC-4400
4.2.2 Logic section components
1) MPU (IC2)
The MPU contains a 16-bit CPU, 1K-bit RAM, 24-bit address bus port, 16-bit data bus port, stepping
motor controller, interrupter controller, A-D converter, I/O ports, and other components.
Built-in CPU
The 16-bit CPU operates in synchronization with a 20 MHz external clock input.
Address bus
The 24-bit address bus port is connected to an 8 M-bit control/CG ROM and printer controller. The
controller/CG ROM synchronizes with the read signals output by the MPU and the 20 MHz clock
signal. The printer controller then selects the chip.
Data bus
Like the address bus, the 16-bit data bus port is connected to the 8 M-bit control/CG ROM and printer
controller.
Stepping motor controller
The stepping motor controller outputs double 1-2 phase exciter drive signals to both the carriage motor
driver and paper feed motor driver.
The stepping motor controller can switch the the 4-step peak current value of both motor driver.
Interrupt controller
For external interruption, the MPU has ports P80, 81, 84, 85, and 87 to receive the POWER button
on/off switching, data reception, initial interrupt request, receive buffer-full warning, and other signals.
The MPU executes interrupt processing for the respective signals.
A-D converter
The following analog signals are detected after they pass through the built-in A-D converter:
AN0: The printer's internal temperature is detected by the thermistor on the logic board.
AN1: The head temperature is detected by the head temperature sensor in the BJ cartridge.
AN3: The head rank is detected by the rank resistor in the BJ cartridge.
I/O port
The setting status determined by the head ID, paper end sensor, home position sensor, and pick-up
roller sensor are input through the input ports. The buzzer, BJ cartridge detection, head-driving voltage
control, and other signals are output from the output ports.
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