Agorobots - Wednesday plan

A more complicated circuit.

You can use a special kind of gate to blink the light on and off:

Now you can see why we wanted 5 volts instead of 6; the chip requires a power supply of 5 volts to operate. This chip can be used for much more than blinking lights, and you will learn how to do it!

Introduction to the PIC.

The chip you used to blink the light is a microcontroller - a microchip that can be used to control things like lights and robots - called the PIC16F627, or PIC for short. Here is the huge technical datasheet for the PIC, in case you are interested in learning about it on your own. The PIC is programmed with a kind of assembly language, the most low-level kind of programming language there is. Here is the program used to make the light blink:

	include "robot.h"

	useoutput portb,3	; use B3 as an output

loop
	bsf	portb,3		; set the output B3
	delay250		; wait 250 ms
	bcf	portb,3		; clear the output B3
	delay250		; wait 250 ms
	goto	loop		; and repeat!

	END

You can download this program from our source directory.

The memory of the PIC.

Inside the PIC, there are two types of memory: program memory, where your program is stored, and data memory, which is used by your program as a general purpose storage space. Some locations in memory are special:

The blocks in this picture represent the bytes (each has eight individual 1s and 0s called bits) of data memory. The large highlighted location at the end of memory is your general storage space, and the small blocks with names are bytes with special functions. An arrow points to the most important ones for building a robot: the input/output bytes. You can see that we used bit number three of portb in the example program above; this is called "port RB3". The other ports, RA0-RA7 and RB0-RB7 are arranged on the chip as in this picture (don't worry about the extra names for some of the port; they indicate features that we probably won't need):

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