Circuit Diagram (2/13) - Oki OKIFAX4550 Maintenance Manual

3.2 46F Circuit Diagram (2/13)
1. Block diagram
46F-PCB circuit diagram (2/13) shown the consists of Flash memory, DRAM, Real time clock IC
and Back up battery circuit.
Figure A.7 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 × 1 (FLS)
Used for work area, report recording etc.
2) DRAM
RAM2 and RAM3: 2MB (512k words × 16 bit) × 2 chips
• 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 date 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 MDMWR-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).
A1 to A19
CASH-N/CASL-N/
RASI-N/RAS2-N
RD-N/WRL-N
MDMRD-N/
MDMWR-N
Figure A.7 Block Diagram of DRAM/Flash Memory and Real-time Clock IC
41309401TH Rev.4
RAM3
2 MB (×16)
RAM2
DRAM
2 MB (×16)
FLS
Flash
memory
1 MB (×16)
IC3
X2
Real time
clock IC
32.768 KHz
Back up
battery
RTCCS
circuit
D0 to D15
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