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Service Guide ML520/521
Chapter 2 Principles of Operation
2.1.01 Main Control Board
The main control board is made up of the microprocessor, peripheral circuits, drive circuits, sensors and
interface connectors.
The power to the main control board is supplied by the transformer assembly through a wire harness.
The power to other electrical parts (line feed motor, space motor and printhead) is provided by the power
supply circuitry through connectors on the main control board.
Microprocessor (MPU) (Location 04C: 67X640)
16 bit MPU, using CMOS technology.
The MPU contains a 20 bit address bus, a 16 bit data bus.
The MPU can access 1 Mbyte of program memory and 1 Mbyte of data memory space.
The microprocessor controls the entire printer by executing the control program through the
LSIs and the driver circuits.
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