Canon MultiPASS C50 Service Manual page 107

a-4) Main ROM (IC301)
This 8 Mbit ROM contains the control programs (e.g. operation panel, scanner and communications
section etc.) for this fax.
a-5) SRAM (IC 302)
This 256 Kbit SRAM is backed up by lithium battery. SRAM holds data registered for system control
and communications management information. Also, SRAM stores contact sensor LED light-on time
data.
a-6) DRAM (IC 303, IC 307)
Two 4 Mbit DRAMs are used as memory for storing image data, and as an MPU work area.
b) Communication control section
b-1) Modem IC (IC 701)
A Rockwell R144EFXL PQFP is used as the modem IC. The MODEM IC carries out G3 modulation
conforming to ITU-T standards V.27ter, V.29, V.17 and V.33 on transmitted data received from the
MPU during transmission. During reception, the MODEM IC carries out G3 modulation on received
signals from the telephone line, according to the same standards.
c) Document scanning section
c-1) System controller IC (IC 401)
The system controller IC include image processing function (UHQ) are as follows:
• A/D conversion
Input signals from the contact sensor are A/D converted.
• Generation of shading data (RGB color & Black and white)
• ABC (Auto Background Control)
Sets the slice level for each scan line.
• Edge enhancement processing
• Binaryzation processing
• Halftone processing
c-2) SRAM (IC 402, IC406)
Two 256 Kbit SRAMs are used as a buffer for the image processing data and shading correction data.
c-3) Color image processing IC (IC 902)
The main functions of the color image processing IC are as follows:
• Color image processing acceleration
Processes the RGB data read during color copying into CMYK print data using high-speed
conversion.
• Contact sensor LED control
• Document feed motor control
c-4) SRAM (IC 901)
This 256 Kbit SRAM is used as a buffer for the color image processing data.
Chapter 2: Technical Reference
2-27