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 co-processor and has the following functions.
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
8-MB DRAM is installed on the video controller PCB.
72 pin DIMM of 4-MB, 8-MB or 16-MB can be installed in the 2 slots on the PCB.
e. ROM DIMM
4-MB ROM is installed on the video controller PCB. In addition, a ROM is installed on the
firmware ROM DIMM. The ROM DIMM is installed in the connector J4 on the video controller
PCB.
The user can install 4-MB or 8-MB ROM DIMM in the left connector J2 and the middle con-
nector J3. The right connector J4 is exclusively for the firmware ROM DIMM.
f. EEPROM (IC11)
The EEPROM has a memory capacity of 4-KB and is used to store the factory default values and
values modified by the control panel.
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CHAPTER 2