Oki OKIOFFICE44 Service Manual page 266

A3.1.3 R44 Circuit Diagram
1. Block diagram
The circuit diagram consists of Flash memory, Mask ROM, DRAM, Real time clock IC and Back
up battery circuit.
Figure A3.1.3 shows the block diagram of Flash memory, Mask ROM, DRAM and Real time
clock.
2. Function
1) Flash memory (FLS1)
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.
• 512 KByte Flash memory x 1 (FLS)
2) Mask ROM
3) DRAM
512 KByte DRAM x 2 (RAM1 and RAM2)
• Used as follows:
4) Back-up battery circuit
The non-rechargeable lithium battery supplies voltage to a real-time clock IC at AC main
interruption.
5) 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 (AD00 -
AD03), 4-bit address bus (A01 - A04) 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).
Board Descriptions
Used for work area, report recording etc.
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.
A - 24 OKIOFFICE 44 Serv. Man., P/N 59276801