The capacity of ROM is 256 Kbit
and
contains the program for system
execution.
The chip
select
condition is as
shown below.
Power Supply Circuit
The power supply circuit has
a voltage regulator
and an APO
(Auto
Power
Off) circuit.
When
power is ON and at the normal
operation, the APO
signal from the CPU
keeps "H" level.
Transistors
T4
and
T8 turn on, so that voltages
VH, VLl, VL2
and VE are provided
to
the
circuits.
When the keyboard is not operated
for seven minutes,
the APO signal
becomes "L" level.
Transistors T4
-
T8 turn off causing
the voltages
to
shut
off.
Voltages VA (5V) and VDD1
(ground) are always provided
to the CPU even
at the APO.
Transistors T1
,
T2 and T3
form
a voltage regulator.
Using the LEDs characteristic
of current
regulation,
T1 stabilizes the battery voltage
at 5V and the darlington-connected
T2
and
T3
amplifies the current.
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