Oki OKIFAX 5400 Maintenance Manual page 284

A3.1.2 E17 Circuit Diagram
1. Block diagram
The circuit diagram shown on page 2/16 consists of Flash memory, Mask ROM, IC3 (Real
time clock IC) and Back up battery circuit.
Figure A3.1.2 shows the block diagram of Flash memory, Mask ROM 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.
• 256 KByte x 16 bit Flash memory x 1 (FLS)
2) Back-up battery circuit
• The non-rechargeable lithium battery supplies voltage to real-time clock IC at AC
3) 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 (AD0 - AD3), 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).
4) MASK
• 256 KByte x 16 bit Flash memory or Mask ROM x 1 (MASK)
A0 to A18
RMCS1-N/
RMCS0-N
MDRD-N/
MDWR-N
Figure A3.1.2 Block Diagram of FLS, MASK and Real Time Clock
40838301TH Rev.1
Used for work area, report recording etc.
main interruption.
Used for program storage
A0 to A3
X2
32.768KHz
MASK
FLS
AD0 to
AD3
IC3
Back-up
battery
circuit
A3 - 3
E17
AD0 to AD15