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CHAPTER 2
VI. OVERALL CONTROL SYSTEM
A.Video Controller PCB
1. Outline
The video controller PCB receives print data consisting of code or image data sent from the exter- nal device (host computer, etc.) through the interface cable.
The print data including the contents specified by the control panel is analyzed, processed and converted into the dot data within this PCB. The dot data is sent to the engine controller PCB to turn ON/OFF the laser diode.
Figure 2-6-1 shows the location of the ICs on this PCB and Figure 2-6-2 shows the block dia- gram.
2. Functions by block a. CPU (IC15)
The CPU is Motorola made 32 bit RISC microprocessor (PPC603e) and its operation frequency is 100MHz. The CPU controls the operation of the video controller PCB according to the control program stored in the ROM.
b. ASIC (IC21)
The ASIC is a graphic
1)DRAM control
2)ROM control
3)Video interface control
4)IEEE 1284 parallel port interface control
5)I/O bus interface support
c. AIR (IC2)
The smoothing control circuit and SRAM are built in the AIR.
Its main functions are as follows.
1)Image smoothing control
2)EEPROM control
3)Control panel interface control
d. DRAM
72 pin DIMM of
e. ROM DIMM
The user can install
f.EEPROM (IC11)
The EEPROM has a memory capacity of
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