PIC Tutorial Main Board Three
Main Board Three
This is the circuit of the third main board for the tutorials, it consists of the PIC16F877, a 7805 regulator, a 20MHz crystal, 6 capacitors, five ten pin connectors, one for PortA, one for PortB, one for PortC, one for PortD and one for PortE . Each of the five ten pin connectors is wired identically, with a ground connection at the left side, and a 5V connection at the right - this will allow you to plug the same extension board into any port, and help to demonstrate their differences - the most obvious differences are that PortA only has 6 I/O lines, which can be either digital I/O or analogue inputs, with 10 bit resolution, and that Port E only has 3 I/O lines.
Basically it's very similar to the 16F628 tutorial board, but has extra ports and added facilities - as the 16F877 doesn't have an internal oscillator a crystal is required for the clock oscillator - I choose a 20MHz crystal for this, if you can't get a 20MHz chip the 4MHz 16F877's seem perfectly happy to run at 20MHz - I suspect they are exactly the same chip, and graded to provide the two different versions.
I used a 100mA regulator IC, a 78L05 - because I happened to have one, but a 7805 1A regulator would do just as well, and give more power availability for extension boards.