Technical pages
16 bits PIC and dsPIC assembler
Instructions
Use
Example
Principle
The assembler is a compiler which
allows to write a program by using the specific instructions of
the microprocessor being of use as the computer core. The
assembler is indispensable to the writing of the basic instructions
of high-level languages (FORTH, Pascal, C, ...) which are so independent
from the used platform themselves. To speak more technical, high-level
languages are portable while the assembler is not it (unless realize
a simulation software).
The purpose of this page is not to
list all the instructions of 16 bits PIC and dsPIC processors or to
give a manual of it. All that is available in the builder website MICROCHIP.
On the other hand, the contents of
this page will allow developers the most warned to realize their
own programs in assembler in the environment of the micro system.
Instructions
- RAZ_ASSEMBLEUR -
Allows to initialize again the labels table
- ASSEMBLEUR -
Assembly of the text which follows this instruction
until the directive " END "
- [>" chemin/nom" -
Allows to generate a assembled source file for the FORTH micro system.
- FORGET_ASSEMBLEUR -
Allows to remove the instructions set dedicated
to the assembler from the vocabulary.
Use
The micro system assembler, only usable with the FORTH Core, is a real
assembler 2 passes managing a labels table. As indicated in the
corresponding column, it contains only 4 instructions FORTH:
- RAZ_ASSEMBLEUR erases the labels
table. This disappearance is automatically realized in the software
installation. It is necessary to execute this
instruction at the beginning of the code source because, in case
of assembly again, he will avoid the appearance of the message
"Etiquette déjà déclarée"(Label already declared).
- ASSEMBLER crosses the interpreter
FORTH in assembler. From this instruction, the syntax of the
following lines has to follow that of the assembler until the
appearance of the directive " END " which indicates
to the assembler to return to mode interpretation FORTH at the
conclusion of the second pass.
- [>" allows to generate a assembled source file for the FORTH micro system for enhance its real time vocabulary.
- FORGET_ASSEMBLEUR frees memory occupied
by the assembler when this one is not useful any more. The 4 FORTH instructions bound to the assembler will disappear
of the vocabulary at the same time as the liberation of the memory
space.
Labels have necessarily to begin with
a major letter. The following characters can be major letters, numbers or
character "_". Not any label has to begin with the same
letters as the registers of processors.
- PIC24x registers: W0 (ou WREG), W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14 (ou WFP), W15 (ou WSP),
PC, SR,TBLPAG,PSVPAG.
- dsPIC3x supplementary registers: A,B.
- PIC24E and dsPIC33E supplementary registers: DSRPAG and DSWPAG unstead of PSVPAG.
The registers of the FORTH micro system PIC and dsPIC are used in the following way:
Instructions must be written in major letters.
Syntax is the same as MICROCHIP. The addressing modes
are the following ones:
- PIC: Wn; [Wn]; [Wn--]; [Wn++]; [--Wn]; [++Wn]; [Wn+Wm]; [Wn+lit]; f; #lit; #bit; Expr; rPAG.
- dsPIC supplements: Acc; Wn*Wn; Wn*Wm; [Wn+=d]; [Wn-=d].
There is an assembly directive allowing to filter the instructions function of the choosen core:
- PIC24F or PIC24H (default core),
- PIC24E,
- DSPIC30F or dsPIC33F,
- DSPIC33E.
Example
To illustrate this presentation, nothing
is worth a good example. This one is available under shape of text file: sqrt_source.txt.
It is about a program allowing the
origin of the square root of an unsigned 16 bits integer (SQRT) and 32 bits (DSQRT).
The result is the file sqrt.txt downloadable in the FORTH micro system via its communication serial link.
