Printer Mechanisms

Let’s try to understand printer hardware. The printer hardware can be categorized into three parts:
1. Controller
2. Video Interface
3. Engine
Controller Operation
Computer sends data to controller board and it converts it into image data. For example when the letter “A” is sent by the computer, controller receive the character code and compares it with its built in font data and decides which image should be printed for the coming signal. After all of the image data of the page has been created inside of the controller, the data is then transmitted to the engine. The controller takes out data from image data for one line then transmits it to the engine through the video interface. The line of data which is taken out is called raster data. The raster data is transmitted to the engine through the video interface. Controller has CPU, Program ROM, Font ROM, Option RAM and smoothing circuit. Also it has an operation unit.
Video Interface
Video interface has following functions:
Function1: To transmit raster data to the printer engine at a fixed speed. It transmits raster data of one line. Transmission speed is fixed depending on the specifications of each engine. For raster data information refer to section 2.
Function 2: To convey the status of the engine to the controller. It conveys the ready status for printing, paper size and completion of printing etc.
Function 3: To convey the controller request, it conveys the request for printing, desired paper size, position and diameter of dots for smoothing.
Engine Operation
Engine board sends the controller processed data to the laser chip as a writing signal. The laser beam forms an latent (electrostatic imgae on the drum attracting toner. The toner is transferred to the paper in transfer section and toner is fused in the fusing section as it passed through the hot roller and pressure roller.