Standard version:-

The basic circuit for the standard development board is illustrated above.

The PIC16F84 microcontroller is designated as IC1, and is shown together with the components which allow it to be programmed from the computer, using the MPASM software. The physical pinout diagram for the PIC16F84 is shown on the PIC16F84 Specifications page of this Reference section.

To program IC1, a 12V to 14V supply is switched by S1 to its control pin 4. The LED D1 indicates when S1 is switched on. In non-programming mode, pin 4 is held at about 4.4V via diode D2.

Switch S2 is the Reset control, pressing it on takes IC1 pin 4 to 0V, holding the chip reset. Resistor R2 protects the power lines at this time.

Switches S3 and S4 are intended for switching the computer's printer port data lines D0 and D1 in and out of circuit with IC1 pins 12 and 13. This option prevents any possibility of the two sets of data lines affecting each other when the PICmicro MCU is actually running a program.

The PICmicro MCU is programmed with a stream of serial data (not parallel). Line D0 carries the data, line D1 carries the clock signal.

An RC (resistor-capacitor) oscillator is used as the PICmicro MCU's clock source. The frequency generated is variable by preset potentiometer VR1 across a range determined by capacitors C1 and C3. Different frequency settings will be used at various stages throughout these tutorials.

Capacitor C3 is only used in the early tutorial sections in order to severely slow down the rate at which individual PICmicro MCU instructions are performed. It will later be removed to increase the operational rate; you will be told when.

Although the circuits and printed circuit board have been designed specifically for these tutorials, the standard development board can be used as a simple test bed when prototyping your own PIC16F84 designs in the future.

External components can readily be connected to the PICmicro MCU's input/output pins via individual wires. The ability to plug the optional LED and LCD modules in and out will also prove to be of great benefit.