Reference Guide

The Development Library 6-39
Example of an ARM assembly language program using the MASD compiler
"!NO CODE !RPL ( turn into RPL mode)
:: ( open a RPL program )
TURNMENUOFF ( remove the menu line )
CODE
% open an assembly program
% this program takes control of the screen and
% displays a Mandelbrot set using the standard algorithm
% ie: for each point from x=-1.5 to 0.5,
% for each point from y=-1 to 1
% if any an, n<256 in the series
% a0=x+iy (complex number), an+1=a0+an²
% has an absolute value > 2, the point is not part of the set
% the numbers are stored on 32 bits.
% the numbers are shifted by 12 bits, the lower 12 bits representing
% the decimal part of the number (in 1/4096)
SAVE % save the RPL pointers
INTOFF % disable keyboard interrupts
SKUB { % jump over the ARM code
*start
!ARM % switch to ARM mode
STMDB sp! {R4 R5 R6 R7 R8 LP} % save registers in the stack
LDR R2, [R1, #2324] % load R2=x (content of saturn
% reg B, nibbles 0-7)
LDR R3, [R1, #2340] % load R3=y (content of saturn
% reg B, nibbles 0-7)
MOV R7 R2 % copy X in r7
MOV R8 R3 % copy Y in r8
MOV R6 256 % copy 256 in R6
{
MUL R4, R2, R2 % r4= x² << 12
MOV R4 R4 >> 12 % r4= x²
MUL R5, R3, R3
MOV R5 R5 >> 12 % r5= y²
ADD LP R4 R5 % LP = x² + y²
CMP LP $4000 % if abs² an > 4
EXITGT % exit
SUB R4 R4 R5 % r4= x²-y²
MUL R3 R2 R3 % R3= X*Y
ADD R2 R7 R4 % r2= X + x²-y² = new x
MOV R3 R3 >> 11 % r3= x*y*2
ADD R3 R8 R3 % r3= Y+2*x*y = new Y
SUBS R6 R6 1 % decrement loop counter
UPNE % up if not 0
% we have looped 256 times and abs(An)<2, the point is in the set!
LDRB R6 [R1 2408] % clear the flag ST0
BIC R6 R6 1
STRB R6 [R1 2408]
LDMIA sp! {R4 R5 R6 R7 R8 PC} % restore all registers and return
}
% we have reached a An where abs(An)>2,the point is out of the set