hexed/hexed.s

   1 ##################################################
   2 #                                                #
   3 # Assemble with gas                              #
   4 #   --register-prefix-optional --bitwise-or      #
   5 #                                                #
   6 ##################################################
   7
   8 .text
   9 .globl main
  10
  11 ##################################################
  12 #                                                #
  13 #        Register and bitmask definitions        #
  14 #                                                #
  15 ##################################################
  16
  17 .equ GFXDATA,           0xc00000
  18 .equ GFXCNTL,           0xc00004
  19
  20 .equ VDP0_E_HBI,        0x10
  21 .equ VDP0_E_DISPLAY,    0x02
  22 .equ VDP0_PLTT_FULL,    0x04
  23
  24 .equ VDP1_SMS_MODE,     0x80
  25 .equ VDP1_E_DISPLAY,    0x40
  26 .equ VDP1_E_VBI,        0x20
  27 .equ VDP1_E_DMA,        0x10
  28 .equ VDP1_NTSC,         0x00
  29 .equ VDP1_PAL,          0x08
  30 .equ VDP1_RESERVED,     0x04
  31
  32 .equ VDP12_SPR_SHADOWS, 0x08
  33 .equ VDP12_SCREEN_V224, 0x00
  34 .equ VDP12_SCREEN_V448, 0x04
  35 .equ VDP12_PROGRESSIVE, 0x00
  36 .equ VDP12_INTERLACED,  0x02
  37 .equ VDP12_SCREEN_H256, 0x00
  38 .equ VDP12_SCREEN_H320, 0x81
  39
  40 .equ VDP16_MAP_V32,     0x00
  41 .equ VDP16_MAP_V64,     0x10
  42 .equ VDP16_MAP_V128,    0x30
  43 .equ VDP16_MAP_H32,     0x00
  44 .equ VDP16_MAP_H64,     0x01
  45 .equ VDP16_MAP_H128,    0x03
  46
  47
  48
  49 ##################################################
  50 #                                                #
  51 #                   MACROS                       #
  52 #                                                #
  53 ##################################################
  54
  55
  56 /* Write val to VDP register reg */
  57 .macro write_vdp_reg reg val
  58         move.w #((\reg << 8) + 0x8000 + \val),(a3)
  59 .endm
  60
  61
  62 /* For immediate addresses */
  63 .macro VRAM_ADDR reg adr
  64         move.l #(((0x4000 + (\adr & 0x3fff)) << 16) + (\adr >> 14)),\reg
  65 .endm
  66
  67
  68 # make VDP word from address adr to d0
  69 # destroys d7
  70 .macro VRAM_ADDR_var adr
  71         move.l \adr,d0
  72         move.l \adr,d7
  73         and.w #0x3fff,d0
  74         lsr.w #7,d7
  75         lsr.w #7,d7
  76         add.w #0x4000,d0
  77         lsl.l #7,d0
  78         lsl.l #7,d0
  79         lsl.l #2,d0
  80         or.l d7,d0
  81 .endm
  82
  83
  84 .macro CRAM_ADDR reg adr
  85         move.l  #(((0xc000 + (\adr & 0x3fff)) << 16) + (\adr >> 14)),\reg
  86 .endm
  87
  88
  89 /* For indirect (variable) addresses */
  90 .macro CRAM_ADDR_var reg adr
  91         move.l \adr,d6
  92         move.l \adr,d7
  93         and.w #0x3fff,d6
  94         lsr.w #7,d7
  95         lsr.w #7,d7
  96         add.w #0xc000,d6
  97         lsl.l #7,d6
  98         lsl.l #7,d6
  99         lsl.l #2,d6
 100         or.l d7,d6
 101         move.l d6,\reg
 102 .endm
 103
 104
 105 .macro VSCROLL_ADDR reg adr
 106         move.l  #(((0x4000 + (\adr & 0x3fff)) << 16) + ((\adr >> 14) | 0x10)),\reg
 107 .endm
 108
 109
 110 .macro HSCROLL_ADDR reg adr
 111         move.l #(((0x4000 + (\adr & 0x3fff)) << 16) + (\adr >> 14)),\reg
 112 .endm
 113
 114
 115 #################################################
 116 #                                               #
 117 #                    DATA                       #
 118 #                                               #
 119 #################################################
 120
 121 colors:
 122         dc.w 0x0000,0x0eee
 123 colors_end:
 124
 125 # pattern:
 126
 127
 128 sprite_data:
 129         /*         Y        size     link          attr        X */
 130         dc.w       0;  dc.b 0x05;  dc.b 0;  dc.w 0x6002;  dc.w 0
 131 sprite_data_end:
 132
 133 hello:
 134         .ascii  "hello world"
 135
 136 ##################################################
 137 #                                                #
 138 #               MAIN PROGRAM                     #
 139 #                                                #
 140 ##################################################
 141
 142 .align 2
 143
 144 main:
 145         /* Initialize VDP */
 146         jsr             init_gfx
 147
 148         /* Load color data */
 149         movea.l         #0,a3
 150         movea.l         #colors,a4
 151         moveq.l         #(colors_end-colors)/2,d4
 152         jsr             load_colors
 153
 154         /* load patterns */
 155         movea.l         #0,a3
 156         movea.l         #font,a4
 157         move.l          #128,d4
 158         jsr             load_tiles
 159
 160         /* generate A layer map */
 161         movea.l         #0xe000,a6
 162         move.l          #28-1,d4
 163 lmaploop0:
 164         movea.l         a6,a3
 165         jsr             load_prepare
 166
 167         move.l          #64/2-1,d3
 168 0:      move.l          #0x00000000,(a3)
 169         dbra            d3,0b
 170
 171         add.l           #64*2,a6
 172         dbra            d4,lmaploop0
 173
 174         /* generate B layer map */
 175         movea.l         #0xc000,a3
 176         jsr             load_prepare
 177
 178         move.l          #64*28/2-1,d3
 179 0:      move.l          #0x00000000,(a3)
 180         dbra            d3,0b
 181
 182         /* upload sprite data */
 183         movea.l         #0xfc00,a3
 184         jsr             load_prepare
 185         movea.l         #sprite_data,a0
 186
 187         move.l          #(sprite_data_end-sprite_data)/2-1,d3
 188 0:      move.l          (a0)+,(a3)
 189         dbra            d3,0b
 190
 191         jsr             wait_vsync
 192
 193         movea.l         #hello,a0
 194         moveq.l         #1,d0
 195         moveq.l         #1,d1
 196         jsr             print
 197
 198 ##################################################
 199 #                                                #
 200 #                 MAIN LOOP                      #
 201 #                                                #
 202 ##################################################
 203
 204 forever:
 205
 206
 207         jsr             wait_vsync
 208         bra             forever
 209
 210
 211
 212 #################################################
 213 #                                               #
 214 #         Initialize VDP registers              #
 215 #                                               #
 216 #################################################
 217
 218 init_gfx:
 219         move.l          #GFXCNTL,a3
 220         write_vdp_reg   0,(VDP0_E_DISPLAY | VDP0_PLTT_FULL)
 221         write_vdp_reg   1,(VDP1_E_VBI | VDP1_E_DISPLAY | VDP1_E_DMA | VDP1_RESERVED)
 222         write_vdp_reg   2,(0xe000 >> 10)        /* Screen map a adress */
 223         write_vdp_reg   3,(0xe000 >> 10)        /* Window address */
 224         write_vdp_reg   4,(0xc000 >> 13)        /* Screen map b address */
 225         write_vdp_reg   5,(0xfc00 >>  9)        /* Sprite address */
 226         write_vdp_reg   6,0
 227         write_vdp_reg   7,0                     /* Backdrop color */
 228         write_vdp_reg   10,1                    /* Lines per hblank interrupt */
 229         write_vdp_reg   11,0                    /* 2-cell vertical scrolling */
 230         write_vdp_reg   12,(VDP12_SCREEN_V224 | VDP12_SCREEN_H320)
 231         write_vdp_reg   13,(0x8000 >> 10)       /* Horizontal scroll address */
 232         write_vdp_reg   15,2
 233         write_vdp_reg   16,(VDP16_MAP_V32 | VDP16_MAP_H64)      /* layer size */
 234         write_vdp_reg   17,0
 235         write_vdp_reg   18,0xff
 236         rts
 237
 238
 239
 240 #################################################
 241 #                                               #
 242 #        Load tile data from ROM                #
 243 #                                               #
 244 # Parameters:                                   #
 245 #  a3: VRAM base                                #
 246 #  a4: pattern address                          #
 247 #  d4: number of tiles to load                  #
 248 #  Destroys a2,d0,d7...                         #
 249 #                                               #
 250 #################################################
 251
 252 load_tiles:
 253         move.l          #GFXCNTL,a2
 254         VRAM_ADDR_var   a3
 255         move.l          d0,(a2)
 256         lsl             #3,d4
 257
 258         move.l          #GFXDATA,a3
 259         subq.l          #1,d4
 260 _copy_tile_data:
 261         move.l          (a4)+,(a3)
 262         dbra            d4,_copy_tile_data
 263
 264         rts
 265
 266
 267 # Prepare to write to VDP RAM @a3
 268 #  a3: VRAM base
 269 #  a3 set to VDP data port for convenience
 270 #  destroys a2,d0,d7
 271
 272 load_prepare:
 273         move.l          #GFXCNTL,a2
 274         VRAM_ADDR_var   a3
 275         move.l          d0,(a2)
 276         move.l          #GFXDATA,a3
 277
 278         rts
 279
 280
 281 #################################################
 282 #                                               #
 283 #        Load color data from ROM               #
 284 #                                               #
 285 # Parameters:                                   #
 286 #  a3: CRAM base                                #
 287 #  a4: color list address                       #
 288 #  d4: number of colors to load                 #
 289 #                                               #
 290 #################################################
 291
 292 load_colors:
 293         move.l          #GFXCNTL,a2
 294         CRAM_ADDR_var   d0,a3
 295         move.l          d0,(a2)
 296
 297         move.l          #GFXDATA,a3
 298         subq.w          #1,d4
 299 _copy_color_data:
 300         move.w          (a4)+,(a3)
 301         dbra            d4,_copy_color_data
 302
 303         rts
 304
 305 #################################################
 306 ##
 307 ## print
 308 #   a0 - string
 309 #   d0 - x
 310 #   d1 - y
 311
 312 print:
 313         lsl.w           #6,d1
 314         add.w           d1,d0
 315         movea.l         #0xe000,a6
 316         lsl.w           #1,d0
 317         add.w           d0,a6
 318         moveq.l         #0,d1
 319
 320 _print_loop:
 321         move.b          (a0)+,d1
 322         beq             _print_end
 323
 324         move.l          a6,a3
 325         jsr             load_prepare
 326         move.w          d1,(a3)
 327         addq.l          #2,a6
 328         jmp             _print_loop
 329
 330 _print_end:
 331         rts
 332
 333
 334 #################################################
 335 #                                               #
 336 #       Wait for next VBlank interrupt          #
 337 #                                               #
 338 #################################################
 339
 340 wait_vsync:
 341         movea.l         #vtimer,a0
 342         move.l          (a0),a1
 343 _wait_change:
 344         stop            #0x2000
 345         cmp.l           (a0),a1
 346         beq             _wait_change
 347         rts
 348
 349
 350 #################################################
 351 #                                               #
 352 #                 RAM DATA                      #
 353 #                                               #
 354 #################################################
 355
 356 .bss
 357
 358 # used by sega_gcc.s
 359 .globl htimer
 360 .globl vtimer
 361 .globl rand_num
 362 htimer:         .long 0
 363 vtimer:         .long 0
 364 rand_num:       .long 0
 365
 366 #
 367
 368 .end
 369
 370 # vim:filetype=asmM68k