Oki OKIOFFICE84, Maintenance Manual

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R51
40672201TH Rev. 4 A3 - 2
A3.1.2 R51 Circuit Diagram (Page 2/12)
1. Block diagram
The circuit diagram shown on page 2/12 consists of Flash memory, DRAM, Real time
clock IC and Back up battery circuit.
Figure A3.1.2 shows the block diagram of Flash memory, DRAM and Real time clock.
2. Function
1) Flash memory (FLS)
Flash memory (electrically erasable and programmable device) is used for the
main software program, which is stored in EP-ROM of the current OKIFAX. Other
than the function of
EP-ROM, Flash memory is also used for the user data
area instead of SRAM chips.
• 1M Byte Flash memory x 1 (FLS)
Used for work area, report recording etc.
2) DRAM
RAM2: 2MB (x16) and RAM3: 0.5MB (x16)
•
Used as follows:
Picture memory for the ECM send/receive mode.
Picture memory for the memory transmission mode.
Picture memory for the retransmission mode.
Picture memory for the reception in memory.
Editing for report printing.
3) Back-up battery circuit
The non-rechargable lithium battery supplies voltage to a real-time clock IC at AC
main interruption.
4) Real-time clock IC (IC3)
IC3 is a real-time clock IC used as a timepiece to display the data and time in year,
month, day, hour, minute, and second units. Its input/output signals are the 4-bit
data bus (D0 - D3), 4-bit address bus (A1 - A4) and the control signals, RTCCS,
MDMRD-N and MDWR-N which perform a CPU-controlled read operation (M/D/Y
H:M, Data read) and write operation (M/D/Y H:M, Data setting).