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2. SCNT BOARD
"SCNT board" is an abbreviation of System CoNTroller board, and per-
forms control of the entire facsimile system. The control functions of the
SCNT board can be broadly classified into the following four control sec-
tions:
2.1
System Control Section
This section comprises an MPU, system controller, memory (SRAM and
DRAM), main ROM, real-time clock (RTC) and other components. A cod-
ing/decoding IC
els. Each of the ICs in the system control section is connected by a
excluding the RTC.
The MPU has a built-in
the CPU. The DMA controller performs DMA transfer between each of
the ICs that require transfer of large amounts of data, for example, between
• System control section
• Communications control section
• Reading control section
• Printer control section
OPCNT board
System controller
MPU
MODEM
NCU board
Telephone line
a) System control section
b) Communications control section
c) Reading control section
d) Printer control section
Fig. 6-2 System Block Diagram
(CODEC
DRAM
Main ROM
SRAM
Image
processor
IC
b)
Contact sensor
IC) is sometimes used on some facsimile mod-
DMA
controller for increasing the efficiency of
FACSIMILE SYSTEM
RTC
SRAM
Address bus
Data bus
a)
Printer
ROM RAM
controller
MPU
c)
d)
SCNT board
Printer
bus
6–3
1
2
3
4
5
6
ït
çi
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