PIC assembly help

I have a few questions about assembly language with PIC. Is there is a commonly used number you can define it like in C like this

But then to assign a memory location to a variable you use something similar

Does this mean you can assign a variable the value 100 and then assign another variable the memory location 0x100?But by default with the PIC isnt 100 = 0x100?

How do you allocate memory locations with PIC in assembly?

I would suggest googling "PIC Tutorial" and reading up on the basics.

But to answer your immediate question:

In MPASM, 100 and 0x100 are the same (both hex 100, or decimal 256). You can specify decimal with a dot in front of the number (e.g. .100 = 100 decimal, or d'100'), or binary (b'10101010').

You can make your code "absolute" or "relocatable" in the assembler. Which way you go is up to you, but relocatable is more flexible, since you don't have to worry about absolute locations; the assembler takes care of this for you.

In absolute mode, you designate fixed locations for each variable:

Then when you use var1 in your code, the assembler substitutes 0x21 for it, so that the instruction points to that address.

In relocatable mode, it's coded like this:


and then the assembler finds available file registers to put var1 and var2 into, and handles assigning them when you reference them.

To answer your other question, about literals vs. addresses, most instructions use file register addresses, so for example:


But there are also "literal" instructions, that work with a literal value:


So it's not how you define your symbols that determines if they're "variables" or "literals", it's how you use them.

To make it easiest transitioning from C, use relocatable mode, declare your variables in udata blocks and just use EQUs for literals.

One last thing: for special function registers (e.g. STATUS, PORTx, etc.), use the include file for the particular PIC you're using, as it will contain EQUs for all the SFRs and other things that will make your code easier to follow.

You must know what are variables & constants!

I don't define them on top of the program.

I'm doing like this.


So you can modify the variables whenever you want.

To assign a memory location I use cblock