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The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 11<br />

Four output bits of an 82C55 set the motor speed. Additional bits set the direction of rotation<br />

and turn the motor on and off by controlling the 555’s RESET input. You can use any output<br />

port bits to control the motor, but logic high inputs at the 4066B must be at least 3.5V, so if<br />

you use NMOS or TTL outputs, add a 10K pull-up resistor from +5V to each port output<br />

that connects to the 4066B.<br />

Listing 11-5 asks you for a motor speed and direction, then causes the motor to spin as<br />

directed.<br />

198 <strong>The</strong> <strong>Microcontroller</strong> <strong>Idea</strong> <strong>Book</strong>

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