; **************************************************************************************************
; **************************************************************************************************
;  THIS WILL NOT RUN ON REAL HARDWARE UNLESS YOU BURN THE NATIVE CODE AT THE BOTTOM
;  OF THIS FILE INTO THE GIGATRONS ROM AT THE CORRECT ADDRESS, EMULATION ONLY!
; **************************************************************************************************
; **************************************************************************************************

vram        EQU     0x0800
x_bounds    EQU     0x9E
y_bounds    EQU     0x76

x_rand      EQU     0x06
y_rand      EQU     0x07
sysFn       EQU     0x22

vbase       EQU     0x40
pixels      EQU     0x42
xx          EQU     0x43
yy          EQU     0x44

                
SYS_DrawPixel2x2_32 EQU     0x2300      ; native code that is defined with either DBR or DWR is written to ROM at this address

        
            LDWI    vram
            STW     vbase

            LDWI    0x0000      
            STW     xx

            LDWI    SYS_DrawPixel2x2_32
            STW     sysFn
            
loop        LD      x_rand      ; x position
            ST      xx
            SUBI    x_bounds    ; works as (x_rand % x_bounds), but only because x_bounds is > 0x00FF/2, fails otherwise
            BLE     y_load
            ST      xx

y_load      LD      y_rand      ; y position
            ST      yy
            SUBI    y_bounds    ; works as (y_rand % y_bounds), but only because y_bounds is > 0x00FF/3, fails otherwise
            BLE     draw
            ST      yy
            SUBI    y_bounds
            BLE     draw
            ST      yy
            
draw        LDW     vbase
            ADDW    xx
            STW     pixels
        
            SYS     32          ; SYS_DrawPixel2x2_32

            BRA     loop        
        
        
; this is a native code routine that is written into ROM using the DBR command, (Define Byte ROM), at the equate defined
; by SYS_DrawPixel2x2_32: this native code is specific to this vCPU module with the input registers that it accepts
SYS_DrawPixel2x2_32     DBR $01 $06 $11 $42 $15 $43 $DE $00 $CE $00 $11 $42 $00 $01 $95 $43 $01 $06 $DE $00 $CE $00 $02 $00 $14 $03 $E0 $CB $00 $F0