3-2
3. ELECTRONICS
EO18-33014
3.2 CPU PC BOARD
This PC board is the central part of the printer, consisting of the following components and circuits:
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CPU
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Flash ROM (4MB)
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SDRAM (8MB)
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D/A Converter and Sensor Sensitivity Adjust Circuit
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Reset Circuit
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PLD (Programmable Logic Device)
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IrDA Interface Driver/Receiver
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Print Head Circuit
(1) CPU
A 32-bit CPU operates by the 30MHz internal clock. (External clock is 5.91MHz.)
This CPU includes 4-KB RAM, 16-bit timer (8 channels), 10-bit A/D converter (8 channels), DMA (4 channels),
serial interface (3 channels), memory interface, etc., and processes the following:
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Controlling the read/write of the SDRAM and flash ROM
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Detecting and controlling the status of the various sensors and switches (Feed gap sensor, black mark
sensor, strip/batch sensor, ambient thermistor, meida cove swtich, and FEED button)
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Communicating with the RS-232C interface or Bluetooth module.
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Controlling the print head circuit
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Detecting the control signal of the stepping motor
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Controlling the status LED
(2) Flash ROM (4MB)
This printer uses a 4MB flash ROM, on which the boot program and application program are written. This
is also used to store the printer settings.
(3) SDRAM (8MB)
This printer uses a 8MB SDRAM, which is used to draw print data.
(4) D/A Converter and Sensor Sensitivity Adjust Circuit
The status signals from the feed gap/black mark sensor, strip/batch sensor, ambiment thermistor, print head
voltage, print head broken element voltage, and print head temperature are sent to the A/D converter of the
CPU. The CPU acknowledges the printer status from these signals and processes the following:
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Controlling the print start position
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Controlling the printer ON/OFF
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Controlling the print pulse
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Detecting the issue mode
Also, the status signals are sent back to each sensor so that the sensor sensitivity can be optimized.
The D/A converter converts these feed back signals from digital to analog, and then outputs them to each
sensors (feed gap/black mark sensor, strip/batch sensor).
(5) Reset Circuit
The reset circuit controls resetting the CPU, PLD, and flash ROM by monitoring the +3.3V.
After the power is turned on and the voltage becomes stable, the reset status of the CPU, PLD and flash ROM
is released. When the power is turned off and the battery voltage drop is detected, the CPU and the flash
ROM are reset to protect the data and the circuit.
(6) PLD (Programmable Logic Device)
This component supports the CPU by processing the following:
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Outputting data to the IrDA interface
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Controlling the Bluetooth module
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Controlling the print head circuit buffer
3.2 CPU PC BOARD
