Video Control System; Interface Controller Pcb - Canon LBP-1120 Service Manual

CHAPTER 2
VI. VIDEO CONTROL SYSTEM
A. Interface Controller PCB
1. Outline
The interface controller receives print information from an external device such as a host computer through an interface
cable.
Print information is divided into two types: CAPT commands used for the printer status and information on the
printer, and dot data that is converted from the resource-typed print data by the host computer.
The dot data is sent to the engine controller circuit, and the engine controller controls the laser diode emission.
The location of the ICs on the interface controller PCB are shown in Figure 2-6-1, and the block diagram is shown
in Figure 2-6-2.
2. Function of Blocks
a. ASIC (IC1)
1) Controls the input/output of the interface controller that comes with a DRAM.
2) Controls the timing of sending the dot pattern data to the engine controller.
3) Performs smoothing, halftone and so on.
b. CPU (IC2)
1) Controls the video interface, USB interface.
2) Processes the serial commands from the video interface.
3) Sends and receives the CAPT commands using the USB interface.
c. DRAM (IC3)
DRAM contains a memory capacity of 512 KB and stores the following information:
1) Dot data converted from image data. (Receive buffer).
d. EEPROM (IC4)
Stores the serial number of the USB interface.
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