remove delay and add iteration limit

[lifeboot.git] / lifeboot.asm

diff --git a/lifeboot.asm b/lifeboot.asm
index 658abe719824f5cc7a97dc2af2ec281ec469289c..9b03696aa827eb2e63b7d2d3c609533fa85b1807 100644 (file)
--- a/lifeboot.asm
+++ b/lifeboot.asm
@@ -1,31 +1,32 @@
 bits 16
-org 0x7c00
+org 7c00h
 
 ; =============================================================================
 
 ; settings --------------------------------------------------------------------
 
 %define DEAD ' '            ; char to represent a dead cell
-%define ALIVE '#'           ; char to represent an alive cell
-%define PRINT_COLOR 0x07    ; grey on black
-%define WAIT_DELAY 0x02     ; 0.131072 seconds
+%define ALIVE '.'           ; char to represent an alive cell
+%define PRINT_COLOR 07h     ; grey on black
+%define ITER_LIM 500        ; reset the simulation after ITER_LIM iterations
 
 ; constants -------------------------------------------------------------------
 
 %define COLS 80
 %define ROWS 25
-%define VGAPGSZ (COLS * ROWS * 2)
+%define VGAPGSZ 1000h
 
 ; memory layout ---------------------------------------------------------------
 
-%define ORG 0x7c00
-%define VGA 0xb8000
+%define ORG 7c00h
+%define VGA 0b8000h
 %define DAT ORG + 512
 
 ; static variables ------------------------------------------------------------
 
 %define xss DAT             ; xs() state (word)
 %define currvgapg DAT + 2   ; current vga page near pointer (word)
+%define iter DAT + 4        ; current iteration # (word)
 
 ; =============================================================================
 
@@ -47,69 +48,68 @@ mov sp, bp
 cld
 
 ; disable cursor
-mov ch, 0x3f                ; cursor start and options
-mov ah, 0x01                ; set text-mode cursor shape
-int 0x10                    ; video services
+mov ch, 3fh                 ; cursor start and options
+mov ah, 01h                 ; set text-mode cursor shape
+int 10h                     ; video services
 
 ; initialize xss
-mov ah, 0x00                ; get
-int 0x1a                    ;  system time
+
+set_xss_seed:
+
+mov ah, 00h                 ; get
+int 1ah                     ;  system time
+
+cmp dx, 0
+je set_xss_seed             ; if seed is 0, xs wont work properly
+
 mov [xss], dx               ; cx:dx = number of clock ticks since midnight
 
 ; initialize currvgapg
-mov word [currvgapg], VGAPGSZ
+mov word [currvgapg], 0
 
 ; start simulation from random state ------------------------------------------
 
 start:
 
 call init_grid
+mov word [iter], 1
 
 ; apply game of life's rules to determine the next state ----------------------
 
 next_state:
 
-call flip_vga_page          ; display current state
-call delay                  ; sleep a little
+call vsync_wait
+call write_next_vga_page
+
+call vsync_wait
+call flip_vga_page
 
-call write_next_vga_page    ; write the next state to the hidden page
+inc word [iter]
+cmp word [iter], ITER_LIM
+jle next_state
 
-jmp next_state
+jmp start                   ; reset
 
 ; =============================================================================
 
 ; functions -------------------------------------------------------------------
 
-; delay() - suspend program execution temporarily -----------------------------
-
-; clobbers ah, cx, dx
-
-delay:
-
-mov cx, WAIT_DELAY          ; cx:dx = interval in microseconds
-mov dx, 0
-
-mov ah, 0x86
-int 0x15                    ; wait
-
-ret
-
 ; vsync_wait() - wait for display to enter the next VBlank cycle --------------
 
 ; clobbers ax, dx
 
 vsync_wait:
 
-mov dx, 0x3da               ; input status #1 register
+mov dx, 3dah                ; input status #1 register
 
 .wait_on:
     in al, dx
-    test al, 0x08           ; vertical retrace bit
+    test al, 08h            ; vertical retrace bit
     jnz .wait_on
 
 .wait_off:
     in al, dx
-    test al, 0x08
+    test al, 08h
     jz .wait_off
 
 ret
@@ -172,13 +172,11 @@ ret
 
 flip_vga_page:
 
-call vsync_wait
-
 xor word [currvgapg], VGAPGSZ   ; flip currvgapg
 setnz al                        ; al = !(currvgapg == 0)
 
-mov ah, 0x05                ; select active display page
-int 0x10                    ; video services
+mov ah, 05h                 ; select active display page
+int 10h                     ; video services
 
 ret
 
@@ -248,7 +246,7 @@ mov byte [bp - 4], -1       ; i = -1
 
         mov dx, [es:si + bx]            ; dl = cell state
 
-        test dl, ALIVE                  ; if (!ALIVE) continue
+        cmp dl, ALIVE                   ; if (!ALIVE) continue
         jne .continue
 
         inc byte [bp - 3]               ; neighbours++
@@ -288,20 +286,20 @@ shl bx, 1
 
 mov dx, [es:si + bx]        ; dl = cell current state
 
-test dl, ALIVE              ; if (ALIVE) {
+cmp dl, ALIVE               ; if (ALIVE) {
 jne .else
 
-test ax, 2                  ;     if (n < 2)
+cmp ax, 2                   ;     if (n < 2)
 jl .dead                    ;         return DEAD
 
-test ax, 3                  ;     if (n > 3)
+cmp ax, 3                   ;     if (n > 3)
 jg .dead                    ;         return DEAD
 
 jmp .alive                  ;     return ALIVE
 
 .else:                      ; }
 
-test ax, 3                  ; if (n != 3)
+cmp ax, 3                   ; if (n != 3)
 jne .dead                   ;     return DEAD
 
 .alive:                     ; return ALIVE
@@ -333,7 +331,7 @@ xor cx, cx                  ; i = 0
 call write_next_cell_state
 
 inc cx
-test cx, COLS * ROWS
+cmp cx, COLS * ROWS
 jl .update_loop             ; for i in [0 .. COLS * ROWS - 1]
 
 ret
@@ -349,4 +347,4 @@ jmp halt
 ; =============================================================================
 
 times 510 - ($ - $$) db 0   ; fill remaining bytes with zeroes
-dw 0xaa55                   ; mbr magic byte
+dw 0aa55h                   ; mbr magic byte