PIC Programming 
             in Assembly 
           (http://www.mstracey.btinternet.co.uk/index.htm)
                               Tutorial 1 
                          Good Programming Techniques. 
               Before we get to the nitty gritty of programming the PIC, I think now is a 
               good time to explain some good programming techniques. 
               If you type a ; (semicolon) anywhere in your program, the compiler will 
               ignore anything after it until the carriage return.  This means we can add 
               comments in our program to remind us of what on earth we were doing in 
               the first place.  This is good practice, even for the simplest programs.  
               You may well fully understand how your program works now, but in a few 
               months time, you may be scratching your head.  So, use comments 
               wherever you can – there is no limit. 
               Secondly, you can assign names to constants via registers (more about 
               these later).  It makes it far easier to read in English what you are writing 
               to, or what the value is, rather than trying to think of what all these 
               numbers mean.  So, use real names, such as COUNT.  Notice that I have 
               put the name in capitals.  This makes it stand out, and also means that 
               (by convention) it is a constant value. 
             
               Thirdly, put some kind of header on your programs by using the semi-
               colons.  An example is below: 
                     ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 
                     ; Author :                                                                     ; 
                     ; Date :                                                                        ; 
                     ; Version:                                                                    ; 
                     ; Title:                                                                          ; 
                     ;                                                                                   ; 
                     ; Description:                                                             ; 
                     ;                                                                                   ; 
                     ;                                                                                   ; 
                     ;                                                                                   ; 
                     ;                                                                                   ; 
                     ;                                                                                   ;  
                     ;                                                                                   ;  
                     ;                                                                                   ;  
                     ;                                                                                   ;  
                     ;                                                                                   ; 
                     ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 
             
               Notice that I have made a kind of box by using the semi-colons.  This just 
               makes it look neat. 
             
                Finally, try and document the program on paper as well.  You can either 
                use flow charts or algorithms or anything else you want.  This will help 
                you in writing your program, step by step. 
                 Right, that’s the lecture over with, lets move on to the real stuff. 
                                      
                                      
                                Tutorial 2 
                                The Registers. 
             
                A register is a place inside the PIC that can be written to, read from or 
                both.  Think of a register as a piece of paper where you can look at and 
                write information on. 
                The figure below shows the register file map inside the PIC16F84.  Don’t 
                worry if you haven’t come across anything like this before, it is only to 
                show where the different bits and pieces are inside the PIC, and will help 
                explain a few of the commands. 
             
                                       
           
            First thing you will notice is that it is split into two - Bank 0 and Bank 1.  
            Bank 1 is used to control the actual operation of the PIC, for example to 
            tell the PIC which bits of Port A are input and which are output.  Bank 0 is 
            used to manipulate the data.  An example is as follows: Let us say we 
            want to make one bit on Port A high.  First we need to go to Bank 1 to set 
            the particular bit, or pin, on Port A as an output.  We then come back to 
            Bank 0 and send a logic 1 (bit 1) to that pin.