A3.1.6 Cpu Peripheral Circuits; A3.1.6.1 Memory; A3.1.6.2 Peripheral Elements - Oki OF5900 Maintenance Manual

R76-/R76-2
A3.1.6 CPU Peripheral Circuits

A3.1.6.1 Memory

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A3.1.6.2 Peripheral elements

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OKIFAX 5700/5900
DRAM
Size: 8 Mbytes (4 megabits x 16 bits; One chip)
Drive voltage: 3.3 V
The basic control signal is generated by the bus state controller incorporated in the
CPU.
Flash ROM
Size: 1.5 Mbytes (512K bits x 16 bits + 256K bits x 16 bits; A total of two chips)
Clock
A real-time clock IC (serial I/F) incorporating a crystal oscillator is used. Its basic
frequency is 500 Hz. CPU pins 110 (RTCTXD), 109 (RTCDATA), and 112
(RTCCLK) are used as I/F signal pins. The drive voltage is 3 V and backed up by a
dedicated lithium battery.
Speaker drive circuit
A tone switching output board is used to switch between the 2441 Hz waveforms
output from the LSI chip (IOGA5), issuing various buzzer sounds, key touch sound,
ringing tone and line monitor sounds.
A block diagram is shown below.
MCNT-PCB
IOGA5 Attenuator
MOCN2
MOCN1
MOCN0
Analog
switch
A3 - 12
CN10
AMP
Speaker
0V