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6-4. Initilize IC (Reset circuit)
VDD : Voltage of memory protection battery
To Pin No.60 of CPU
When the voltage level at Pin No.60 of CPU is not stabilized, CPU does not work properly
in rare case. Therefore, this machine uses the initialize IC for stabilizing the voltage.
Even the voltage lebel of VDD(Pin No.2) is changed, Pin No.1 of initilize IC outputs
stabilized 5 volts. When the VDD voltage become less than 1.9V, the initialize IC send a
reset signal to CPU.
6-5. Power down detection circuit (PWD)
To Pin No.64 of CPU
When the VP voltage become less than 4.8V, the pin No.1 of IC5 become "Low" level.
Then,the transistor Q43 become OFF.
When Q43 become OFF, the voltage lebel of pin No.64 of CPU changes to "High" level
from "Low". Then, CPU knows power failure.
6-6. Address latch circuit
CPU uses 8 port (AD0 ~ AD7) for address bus
and data bus.
To select the address, CPU use the IC13.
CPU send the address to IC13, and send ASTB
signal at same time.
Then, IC13 store the address and output the
address immediately.
In this way, CPU select the address and data
signal.
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