Oki OKIOFFICE 84 Service Manual page 384

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.
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1M Byte Flash memory x 1 (FLS)
Used for work area, report recording etc.
2) DRAM
RAM2: 2MB (x16) and RAM3: 0.5MB (x16)
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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).
Service Guide OKIOFFICE 84
Chapter A Board Descriptions
Page: 230