On Tue, 13 Mar 2001, Thomas N wrote:

> Hi everyone,
>
> The PICmicro uses only 35 instructions and I notice there is no "c like"
> instruction, how come people use statement like IF...ELSE, WHILE, MACRO,
> etc.  Where are these instructions?  I can't find these instruction in the
> datasheet.  How much memory does each statement occupy?

The other answers are pretty much al I could tell you.  There are
branching and bit/sign tests in the PIC instruction set, which are used to
implement the C instructions -- or BASIC, FORTH or whatever higher level
language you're using.

> I heard that if I use C language, the memory on the PICmicro won't be
> enough.

It always is for me.  I find I could probably go through the code my C
compiler generates and make it a little smaller, a little more efficent,
whatever.  I have never needed to, since I've never run out of RAM or
program space, or needed tat last few microseconds of execution time.  It
also allows me to write what I need to write much faster than I could if I
were using assembly.  Of course, that's just me.  Assembly fanatics would
think coding in C is a horrible idea, I feel the same way about BASIC...
<grin>

Here's an example:

; ....................  do {
; ....................          lcd_line_2[14] ='F';
 MOVLW  46
 MOVWF  38
; ....................          if(!C_F) lcd_line_2[14] = 'C';
 BTFSC  3B,0
 GOTO   0B0
 MOVLW  43
 MOVWF  38
; ....................          C_F = !C_F;
 MOVLW  01
 XORWF  3B,F
; ....................              putlcd(lcd_line_2);
 MOVLW  2A
 MOVWF  3D
 GOTO   096
; ....................          sleep();
 SLEEP
; ....................          sleep();
 SLEEP
; ....................  } while(1);
 GOTO   0AA

Some lines of C code generate one instruction, some generate 10, 20,
whatever it takes.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
                -- Isaac Asimov

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