Vcc power and gnd ground pins provide power for the

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Unformatted text preview: ted circuits, and to stabilize frequencies for radio transmitters and receivers. VCC (power) and GND (ground) pins provide power for the oscillator circuitry, generating automatically clocks. A circuit symbol of the crystal oscillator is shown in Figure 4.1.4. Figure 4.1.4 Schematic Symbol of Crystal Oscillator 4.1.3 LED Output Circuit LEDs emit light when an electric current passes through them. Figure 4.1.6 illustrates an output circuit of the LED. As LED’s anode (labeled a or +) is connected toward the port, electricity flow through the resistor and the light is on when the port releases ‘high’ current – i.e., a positive voltage is applied to the anode. The resistor between the LED and the port is to limit the current to a safe value. Without this, the LED could be destroyed because too much current will pass through and burn it out. To recap, the port releases ‘high’ current to get an LED to light up; and the LED does not glow when the port sends ‘low’ electrical flow. Figure 4.1.6 LED Output Circuit 4.1.4 PIC16F84...
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This note was uploaded on 11/21/2010 for the course MECHANICAL mae302 taught by Professor Jang during the Spring '10 term at Seoul National.

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