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[Reset Logic schematic]

The Reset Circuit

The output of the exclusive 'or' gate UD3 pin 6 will be "low" until C46 has charged through R25. Once the voltage across C46 reaches 2 volts, the output of UD3 pin 6 will go "high". This occurs when the disk is powered on, or a reset pulse is generated by a device connected to the serial bus. The reset pulse on the serial bus interface is input on, pin 6 of P2 or P3. This "low" to "high" going pulse on pin 6 of UD3 is input to the microprocessors reset interrupt input. This causes a restart on reset routine to be executed giving control of the disk drive operation to the Disk Operating System (DOS).
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This page has been created by Sami Rautiainen.
Read the small print. Last updated September 05, 2020.