Switching options - standard version:-

The switching options and demo LEDs for the standard development board are illustrated above.

The PIC16F84 has two input/output ports, Port A and Port B. Each pin of each port has its own LED. Port A has a set five push-to-make switches, SA0 to SA4.

Resistors R19 to R23 protect the Port A pins from excess current flow if the switches are pressed when the pins are configured as outputs. Resistors R45 to R49 bias Port A pins to 0V. Resistors R6 to R18 are ballast resistors for the LEDs on both ports.

Resistors R32 to R44 protect the ports from excess current flow when they are in output mode and external circuits are connected to the ports via these resistors.

Note that the resistor values have been selected to provide the best circuit protection that is compatible with letting all aspects of the development board function satisfactorily. The values are not necessarily those which would be best suited to a stand-alone design for other applications.

Audio output from RA0 is via capacitor C9, to which a pair of high impedance headphones may be plugged via the socket on the PCB.