Mercurial > repos > blastem
annotate cd_graphics.c @ 2069:8e51c0c3f2e3 segacd
Initial attempt at implementing the Sega CD graphics hardware
author | Michael Pavone <pavone@retrodev.com> |
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date | Sun, 30 Jan 2022 19:55:33 -0800 |
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children | 598017ef4b0d |
rev | line source |
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2069
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Initial attempt at implementing the Sega CD graphics hardware
Michael Pavone <pavone@retrodev.com>
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1 #include "cd_graphics.h" |
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2 #include "backend.h" |
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3 |
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4 void cd_graphics_init(segacd_context *cd) |
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5 { |
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6 cd->graphics_int_cycle = CYCLE_NEVER; |
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7 } |
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8 |
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9 #define BIT_HFLIP 0x8000 |
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10 |
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11 static uint8_t get_src_pixel(segacd_context *cd) |
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12 { |
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13 uint16_t x = cd->graphics_x >> 11; |
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14 uint16_t y = cd->graphics_y >> 11; |
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15 cd->graphics_x += cd->graphics_dx; |
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16 cd->graphics_x &= 0xFFFFFF; |
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17 cd->graphics_y += cd->graphics_dy; |
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18 cd->graphics_y &= 0xFFFFFF; |
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19 uint16_t stamp_shift, pixel_mask; |
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20 uint16_t stamp_num_mask; |
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21 if (cd->gate_array[GA_STAMP_SIZE] & BIT_STS) { |
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22 //32x32 stamps |
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23 stamp_shift = 5; |
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24 pixel_mask = 0x1F; |
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25 stamp_num_mask = 0x3FC; |
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26 } else { |
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27 //16x16 stamps |
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28 stamp_shift = 4; |
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29 pixel_mask = 0xF; |
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30 stamp_num_mask = 0x3FF; |
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31 } |
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32 uint16_t stamp_x = x >> stamp_shift; |
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33 uint16_t stamp_y = y >> stamp_shift; |
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34 uint16_t max, base_mask; |
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35 uint32_t row_shift; |
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36 if (cd->gate_array[GA_STAMP_SIZE] & BIT_SMS) { |
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37 max = 4096 >> stamp_shift; |
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38 base_mask = 0xE000 << ((5 - stamp_shift) << 1); |
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39 //128 stamps in 32x32 mode, 256 stamps in 16x16 mode |
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40 row_shift = 12 - stamp_shift; |
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41 } else { |
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42 max = 256 >> stamp_shift; |
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43 base_mask = 0xFFE0 << ((5 - stamp_shift) << 1); |
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44 //8 stamps in 32x32 mode, 16 stamps in 16x16 mode |
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45 row_shift = 8 - stamp_shift; |
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46 } |
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47 if (stamp_x > max || stamp_y > max) { |
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48 if (cd->gate_array[GA_STAMP_SIZE] & BIT_RPT) { |
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49 stamp_x &= max - 1; |
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50 stamp_y &= max - 1; |
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51 } else { |
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52 return 0; |
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53 } |
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54 } |
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55 uint32_t address = (cd->gate_array[GA_STAMP_MAP_BASE] & base_mask) << 1; |
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56 address += (stamp_y << row_shift) + stamp_x; |
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57 uint16_t stamp_def = cd->word_ram[address]; |
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58 uint16_t stamp_num = stamp_def & stamp_num_mask; |
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59 uint16_t pixel_x = x & pixel_mask; |
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60 uint16_t pixel_y = y & pixel_mask; |
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61 if (stamp_def & BIT_HFLIP) { |
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62 pixel_x = pixel_mask - pixel_x; |
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63 } |
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64 uint16_t tmp; |
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65 switch (stamp_def >> 13 & 3) |
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66 { |
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67 case 0: |
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68 break; |
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69 case 1: |
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70 tmp = pixel_y; |
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71 pixel_y = pixel_x; |
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72 pixel_x = pixel_mask - tmp; |
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73 break; |
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74 case 2: |
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75 tmp = pixel_y; |
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76 pixel_y = pixel_mask - pixel_x; |
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77 pixel_x = pixel_mask - tmp; |
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78 break; |
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79 case 3: |
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80 tmp = pixel_y; |
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81 pixel_y = pixel_mask - pixel_x; |
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82 pixel_x = tmp; |
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83 break; |
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84 } |
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85 uint16_t cell_x = pixel_x >> 4; |
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86 uint32_t pixel_address = stamp_num << 6; |
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87 pixel_address += (pixel_y << 1) + (cell_x << (stamp_shift + 2)) + (pixel_x >> 2 & 1); |
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88 uint16_t word = cd->word_ram[pixel_address]; |
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89 switch (pixel_x & 3) |
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90 { |
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91 default: |
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92 case 0: |
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93 return word >> 12; |
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94 case 1: |
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95 return word >> 8 & 0xF; |
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96 case 2: |
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97 return word >> 4 & 0xF; |
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98 case 3: |
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99 return word & 0xF; |
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100 } |
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101 |
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102 } |
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103 |
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104 enum { |
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105 FETCH_X, |
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106 FETCH_Y, |
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107 FETCH_DX, |
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108 FETCH_DY, |
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109 PIXEL0, |
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110 PIXEL1, |
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111 PIXEL2, |
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112 PIXEL3, |
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113 DRAW |
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114 }; |
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115 |
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116 void draw_pixels(segacd_context *cd) |
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117 { |
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118 uint16_t to_draw = 4 - (cd->graphics_dst_x & 3); |
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119 uint16_t x_end = cd->gate_array[GA_IMAGE_BUFFER_HDOTS] + (cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3); |
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120 if (cd->graphics_dst_x + to_draw > x_end) { |
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121 to_draw = cd->gate_array[GA_IMAGE_BUFFER_HDOTS] + (cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3) - cd->graphics_dst_x; |
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Initial attempt at implementing the Sega CD graphics hardware
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|
122 } |
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Initial attempt at implementing the Sega CD graphics hardware
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|
123 for(uint16_t i = 0; i < to_draw; i++) |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
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|
124 { |
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125 uint32_t dst_address = cd->gate_array[GA_IMAGE_BUFFER_START] << 1; |
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126 dst_address += cd->graphics_dst_y << 4; |
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127 dst_address += cd->graphics_dst_x >> 2 & 1; |
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128 dst_address += ((cd->graphics_dst_x >> 3) * cd->gate_array[GA_IMAGE_BUFFER_VCELLS]) << 4; |
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129 uint16_t pixel_shift = 12 - 4 * (cd->graphics_dst_x & 3); |
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130 uint16_t pixel = cd->graphics_pixels[i] << pixel_shift; |
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131 uint16_t src_mask_check = 0xFF << pixel_shift; |
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132 uint16_t src_mask_keep = ~src_mask_check; |
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133 switch (cd->gate_array[1] >> 3 & 3) |
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|
134 { |
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135 case 0: |
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136 //priority mode off |
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137 cd->word_ram[dst_address] &= src_mask_keep; |
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138 cd->word_ram[dst_address] |= pixel; |
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Initial attempt at implementing the Sega CD graphics hardware
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139 break; |
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140 case 1: |
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parents:
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|
141 //underwrite |
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142 if (pixel && ! (cd->word_ram[dst_address] & src_mask_check)) { |
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143 cd->word_ram[dst_address] &= src_mask_keep; |
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144 cd->word_ram[dst_address] |= pixel; |
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Initial attempt at implementing the Sega CD graphics hardware
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145 } |
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146 break; |
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147 case 3: |
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148 //overwrite |
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149 if (pixel) { |
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150 cd->word_ram[dst_address] &= src_mask_keep; |
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151 cd->word_ram[dst_address] |= pixel; |
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152 } |
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153 break; |
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154 } |
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|
155 } |
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156 cd->graphics_dst_x += to_draw; |
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157 if (cd->graphics_dst_x == x_end) { |
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158 cd->graphics_dst_y++; |
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159 --cd->gate_array[GA_IMAGE_BUFFER_LINES]; |
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160 cd->graphics_step = FETCH_X; |
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161 } else { |
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162 cd->graphics_step = PIXEL0; |
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163 } |
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164 } |
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|
165 |
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166 #define CHECK_CYCLES cd->graphics_step++; if(cd->graphics_cycle >= cycle) break |
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167 #define CHECK_ONLY if(cd->graphics_cycle >= cycle) break |
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168 |
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169 static void do_graphics(segacd_context *cd, uint32_t cycle) |
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170 { |
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171 if (!cd->gate_array[GA_IMAGE_BUFFER_LINES]) { |
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172 return; |
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|
173 } |
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174 while (cd->graphics_cycle < cycle) |
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|
175 { |
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|
176 switch (cd->graphics_step) |
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|
177 { |
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178 case FETCH_X: |
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179 cd->graphics_x = cd->word_ram[cd->gate_array[GA_TRACE_VECTOR_BASE] << 1] << 8; |
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180 cd->graphics_cycle += 3*4; |
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181 cd->graphics_dst_x = cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3; |
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182 CHECK_CYCLES; |
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|
183 case FETCH_Y: |
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184 cd->graphics_y = cd->word_ram[cd->gate_array[GA_TRACE_VECTOR_BASE] << 1 + 1] << 8; |
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185 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
186 CHECK_CYCLES; |
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|
187 case FETCH_DX: |
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|
188 cd->graphics_dx = cd->word_ram[cd->gate_array[GA_TRACE_VECTOR_BASE] << 1 + 2]; |
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|
189 if (cd->graphics_dx & 0x8000) { |
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|
190 cd->graphics_dx |= 0xFF0000; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
191 } |
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Initial attempt at implementing the Sega CD graphics hardware
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|
192 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
193 CHECK_CYCLES; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
194 case FETCH_DY: |
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|
195 cd->graphics_dy = cd->word_ram[cd->gate_array[GA_TRACE_VECTOR_BASE] << 1 + 3]; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
196 if (cd->graphics_dy & 0x8000) { |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
197 cd->graphics_dy |= 0xFF0000; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
198 } |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
199 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
200 CHECK_CYCLES; |
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diff
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|
201 case PIXEL0: |
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|
202 cd->graphics_pixels[0] = get_src_pixel(cd); |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
203 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
204 if ((cd->graphics_dst_x & 3) == 3 || (cd->graphics_dst_x + 1 == cd->gate_array[GA_IMAGE_BUFFER_HDOTS] + (cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3))) { |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
205 cd->graphics_step = DRAW; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
206 CHECK_ONLY; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
207 } else { |
8e51c0c3f2e3
Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
208 CHECK_CYCLES; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
209 } |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
210 case PIXEL1: |
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diff
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|
211 cd->graphics_pixels[1] = get_src_pixel(cd); |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
212 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
213 if ((cd->graphics_dst_x & 3) == 2 || (cd->graphics_dst_x + 2 == cd->gate_array[GA_IMAGE_BUFFER_HDOTS] + (cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3))) { |
8e51c0c3f2e3
Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
214 cd->graphics_step = DRAW; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
215 CHECK_ONLY; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
216 } else { |
8e51c0c3f2e3
Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
217 CHECK_CYCLES; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
218 } |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
219 case PIXEL2: |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
220 cd->graphics_pixels[2] = get_src_pixel(cd); |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
221 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
changeset
|
222 if ((cd->graphics_dst_x & 3) == 1 || (cd->graphics_dst_x + 3 == cd->gate_array[GA_IMAGE_BUFFER_HDOTS] + (cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3))) { |
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Initial attempt at implementing the Sega CD graphics hardware
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|
223 cd->graphics_step = DRAW; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
224 CHECK_ONLY; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
225 } else { |
8e51c0c3f2e3
Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
226 CHECK_CYCLES; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
changeset
|
227 } |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
228 case PIXEL3: |
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diff
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|
229 cd->graphics_pixels[3] = get_src_pixel(cd); |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
230 cd->graphics_cycle += 2*4; |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
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|
231 CHECK_CYCLES; |
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Initial attempt at implementing the Sega CD graphics hardware
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parents:
diff
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|
232 case DRAW: |
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diff
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|
233 draw_pixels(cd); |
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Initial attempt at implementing the Sega CD graphics hardware
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diff
changeset
|
234 cd->graphics_cycle += 1*4; |
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Initial attempt at implementing the Sega CD graphics hardware
Michael Pavone <pavone@retrodev.com>
parents:
diff
changeset
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235 if (!cd->gate_array[GA_IMAGE_BUFFER_LINES]) { |
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236 break; |
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237 } |
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238 CHECK_ONLY; |
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239 } |
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240 } |
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241 } |
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242 |
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243 void cd_graphics_run(segacd_context *cd, uint32_t cycle) |
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244 { |
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245 while (cd->graphics_cycle < cycle) |
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246 { |
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247 if (cd->gate_array[GA_STAMP_SIZE] & BIT_GRON) { |
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248 do_graphics(cd, cycle); |
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249 //end calculation and actual emulated execution time probably don't 100% line up yet |
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250 //deal with that here for now |
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251 for(; cd->graphics_cycle < cycle; cd->graphics_cycle += 4) |
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252 { |
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253 } |
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254 if (cd->graphics_cycle >= cd->graphics_int_cycle) { |
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255 cd->gate_array[GA_STAMP_SIZE] &= ~BIT_GRON; |
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256 break; |
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257 } |
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258 } else { |
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259 cd->graphics_cycle = cycle; |
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260 } |
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261 } |
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262 } |
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263 void cd_graphics_start(segacd_context *cd) |
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264 { |
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265 if (!(cd->gate_array[GA_STAMP_SIZE] & BIT_GRON)) { |
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266 printf("grahpics start @ %u\n", cd->graphics_cycle); |
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267 cd->gate_array[GA_STAMP_SIZE] |= BIT_GRON; |
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268 //Manual scan is bad, but formula appears to be |
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269 // vsize * (13 + 2 * hoffset + 9 * (hdots + hoffset - 1)) |
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270 //with an additional 13? cycle setup cost per line |
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271 uint32_t lines = cd->gate_array[GA_IMAGE_BUFFER_LINES]; |
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272 uint32_t hdots = cd->gate_array[GA_IMAGE_BUFFER_HDOTS]; |
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273 uint32_t hoffset = cd->gate_array[GA_IMAGE_BUFFER_OFFSET] & 3; |
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274 cd->graphics_int_cycle = cd->graphics_cycle + 4 * lines * (13 + 2 * hoffset + 9 * (hdots + hoffset - 1)); |
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275 cd->graphics_dst_y = cd->gate_array[GA_IMAGE_BUFFER_OFFSET] >> 3; |
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276 } else { |
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277 printf("graphics start ignored @ %u\n", cd->graphics_cycle); |
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278 } |
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279 |
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280 } |