Specifications

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9-2. Power supply circuit
1) Power supply circuit for CPU, GATE ARRAY and RAMs.
When the main batteries are set, the voltage (9V) supplies at the terminal VDD1 of CPU (LSI1), GATE
ARRAY (LSI2) and RAM (LSI4).
When IC2 receives a voltage, the regulated voltage (4V) will be applied to the GND lines from the
terminal OUT (Pin No.1).
2) Power supply circuit for ROM
When the GATE ARRAY (LSI2) controls the terminal VOB (Pin No.28) with "L" level, the transistor
2SA1411 (Q3) will be turned ON, then the voltage of the VDD lines will be applied the VCC lines.
The voltage of the ROM (LSI5) is supplied from the VCC lines.
3) Main switch
The CPU (LSI1) detects the informations of the Main switch by the terminal SW (Pin No.36) from the
SWO signal of the GATE ARRAY (LSI2).
4) How to turn the display ON.
When pressing "ON" key under the ON side of the Main switch , the CPU (LSI1) generates the signal
to turn the display ON at the terminal V2ON (Pin No.45).
This signal goes to the terminal VIN (Pin No.24) of the GATE ARRAY (LSI2), then the GATE ARRAY
(LSI2) generates "L" level at the terminal VOB (Pin No.28). When the transistor 2SA1179 (Q2) re-
ceives "L" level, the transistor 2SC2812 (Q1) will be turned ON also. Then LCD drive voltage V1~V4
will be applied.
5) How to detect the voltage for the main batteries.
When the voltage of the VDD lines becomes +6.6V±0.18V, the terminal OUT (Pin No.1) of the detector
RH5V60BA (IC4) becomes "L" level, then this signal goes to the terminal INTO (Pin No.70) of the CPU
(LSI1) and the terminal PDN (Pin No.35) of the GATE ARRAY (LSI2).
The CPU detects the low battery condition, then the display turns OFF.