Canon MultiPASS C755, Service Manual, Page: 136 / 143

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MultiPASS C755 Chapter 3: Maintenance & Service
10.2 Circuit Board Components
a) System control section
The system controller is made up of the following components, and controls the entire fax system. This
section drive +3.3V voltage from power supply unit.
a-1) MPU (Micro Processor Unit) (IC 101)
The main functions of the NEC µPD703102GJ-A33-022-8EU(V850) MPU are as follows.
• 32 bit CPU
• 24 bit address bus
• 16 bit data bus
• DMA control
• A/D converter
• Serial interface
• Software CODEC (MH, MR, MMR, JBIG)
• Color FAX function (Lab color conversion, JPEG encode/decode)
• Interrupt control unit
• Built-in 4K Byte RAM for working area
• Built-in 128K Byte Mask-ROM for programable area
a-2) System controller (IC 301)
The system controller is a gate array for controlling MPU peripheral devices. This IC drive +5V and
+3.3V voltage. The main functions of the system controller are as follows:
• Printer resolution conversion (Ultra-smoothing)
This IC converts facsimile data of horizontal resolution of 8 dots/mm and vertical resolution of 3.85 or
7.7 lines/mm to print data of 360 dpi and 360 dpi, respectively.
• BJ printer interface (IEEE 1284)
8 bit parallel print data sent to the Printer controller.
• OPCNT serial interface (Contains document sensor and document edge sensor signals)
• DRAM/SRAM controller
Controls DRAM/SRAM read/write and renewal.
• Serial-to-parallel conversion
• Horizontal scaling
• Detection of document edge sensor and ink detection sensor
a-3) RTC (Real Time Clock) IC (IC 502)
S-3510ANFJA is used as the RTC. The RTC IC is backed up by lithium battery, and counts the date
and time.