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annotate src/vdp.c @ 19:04fc17376999

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Sort of working tile rendering and tile test ROM
author Michael Pavone <pavone@retrodev.com>
date Mon, 28 Mar 2016 23:43:31 -0700
parents 04d8efe7a1f0
children 91ded3b12d96
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 #include <stdint.h>
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2 #include <string.h>
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3 #include <stdio.h>
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4 #include "vdp.h"
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5 #include "system.h"
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6
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7 void vdp_init(vdp *context, uint32_t clock_div)
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8 {
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9 memset(context, 0, sizeof(vdp));
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10 //clock div specifies the pixel clock divider
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11 //but our emulation step is half that fast
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12 context->clock_inc = clock_div*2;
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13 context->drawbuffer = context->linebuffers;
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14 context->readbuffer = context->linebuffers+320;
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15 }
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16
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17 void vdp_run(vdp *context, uint32_t target)
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18 {
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19 while (context->cycles < target)
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20 {
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21 context->hcounter+=2;
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22 if (context->hcounter == 416) {
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23 context->hcounter = 0;
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24 context->vcounter++;
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25 if (context->vcounter == 262) {
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26 context->vcounter = 0;
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27 }
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28 }
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29 context->status &= ~(VDP_STATUS_VRAM|VDP_STATUS_SRAM);
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30 //Render to linebuffer
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31 if (context->vcounter > 15 && context->vcounter < 240 && context->hcounter < 406) {
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32 if (context->hcounter < 246) {
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33 context->status |= VDP_STATUS_VRAM;
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34 if (!context->hcounter) {
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35 //flip linebuffers
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36 if (context->drawbuffer == context->linebuffers) {
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37 context->drawbuffer = context->linebuffers + 328;
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38 context->readbuffer = context->linebuffers;
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39 } else {
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40 context->drawbuffer = context->linebuffers;
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41 context->readbuffer = context->linebuffers + 328;
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42 }
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43 context->draw_dest = 0;
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44 }
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45 if (context->draw_counter) {
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46 context->draw_counter--;
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47 uint16_t pixels = context->vram[context->draw_source++];
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48 for (int i = 0; i < 4; i++)
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49 {
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50 uint8_t pixel = ((pixels >> ((3-i) * 4)) & 0xF) | context->palpriority;
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51 context->drawbuffer[context->draw_dest++] = pixel;
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52 }
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53 } else {
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54 //00VV VVVV VVHH HHHH
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55 uint16_t vpos = (context->vscroll & 0x7FF) + context->vcounter - 16;
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56 uint16_t vmask = (context->vscroll >> 2) & 0x3E00;
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57 uint16_t vcoarse = (vpos << 3) & 0x3FC0;
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58 uint16_t vfine = vpos & 7;
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59 uint16_t hcoarse = ((context->hscroll >> 3) + context->hcounter/6) & 0x3F;
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60 uint16_t tableaddress = hcoarse | (vcoarse & ~vmask) | ((context->vscroll << 3) & vmask);
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61 //printf("VCounter: %X, VScroll: %X, HCounter: %X, Table: %X\n", context->vcounter, context->vscroll, context->hcounter, tableaddress);
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62 uint16_t entry = context->vram[tableaddress];
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63 context->draw_source = (entry & 0x3FF) * 16;
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64 if (entry & 0x1000) {
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65 context->draw_source += 14 - vfine * 2;
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66 } else {
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67 context->draw_source += vfine * 2;
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68 }
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69 context->palpriority = entry >> 9 & 0x70;
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70 context->draw_counter = 2;
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71 //TODO: handle horizontal flip
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72 }
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73 //TODO: Scan sprite table
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74 } else {
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75 //TODO: Render sprites
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76 }
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77 }
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78 //Draw to framebuffer
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79 if (context->vcounter > 8 && context->vcounter < 249 && context->hcounter < 320) {
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80 if (!context->hcounter && context->vcounter == 9) {
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81 context->framebuffer = system_get_framebuffer(&context->pitch);
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82 //pitch is in terms of bytes, but we want it in terms of pixels
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83 context->pitch /= sizeof(uint16_t);
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84 }
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85 uint16_t *dest = context->framebuffer + (context->vcounter - 9) * context->pitch + context->hcounter;
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86 if (context->status & VDP_STATUS_ENABLED && context->vcounter > 16 && context->vcounter < 241) {
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87 *dest = context->cram[0x3F & context->readbuffer[context->hcounter]];
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88 dest++;
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89 *dest = context->cram[0x3F & context->readbuffer[context->hcounter+1]];
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90 } else {
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91 //Display is disabled or we're in the border area, draw the background color
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92 *dest = *context->cram;
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93 dest++;
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94 *dest = *context->cram;
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95 }
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96 } else if(!context->hcounter && context->vcounter == 249) {
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97 system_framebuffer_updated();
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98 context->framebuffer = NULL;
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99 }
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100 //Handle the FIFO
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101 if (context->status & VDP_STATUS_FIFO) {
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102 switch (context->fifo_dest)
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103 {
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104 case FIFO_DEST_VRAM:
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105 if (!(context->status & VDP_STATUS_VRAM)) {
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106 context->vram[context->dest_offset++] = context->fifo;
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107 context->dest_offset &= sizeof(context->vram)/2-1;
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108 context->status &= ~VDP_STATUS_FIFO;
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109 }
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110 break;
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111 case FIFO_DEST_SRAM:
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112 if (!(context->status & VDP_STATUS_SRAM)) {
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113 context->sram[context->dest_offset++] = context->fifo;
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114 context->dest_offset &= sizeof(context->sram)/2-1;
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115 context->status &= ~VDP_STATUS_FIFO;
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116 }
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117 break;
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118 case FIFO_DEST_CRAM:
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119 context->cram[context->dest_offset++] = context->fifo;
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120 context->dest_offset &= sizeof(context->cram)/2-1;
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121 context->status &= ~VDP_STATUS_FIFO;
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122 break;
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123 }
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124 }
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125 context->cycles += context->clock_inc;
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126 }
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127 }
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128 void vdp_write_address(vdp *context, uint16_t value)
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129 {
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130 context->status &= ~VDP_STATUS_FIFO;
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131 if (!(value & 0x8000)) {
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132 context->fifo_dest = FIFO_DEST_VRAM;
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133 context->dest_offset = (value & (sizeof(context->vram) -1))/2;
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134 } else if ((value & 0xFF00) == 0xFE00) {
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135 context->fifo_dest = FIFO_DEST_SRAM;
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136 context->dest_offset = (value & (sizeof(context->sram) -1))/2;
11
04d8efe7a1f0 Initial stab at video output and background color rendering. Fixed address decoding in address port write handler.
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137 } else if ((value & 0xFF00) == 0xFF00) {
8
5176efdda5ae Initial work on VDP emulation
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parents:
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138 context->fifo_dest = FIFO_DEST_CRAM;
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parents:
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139 context->dest_offset = (value & (sizeof(context->cram) -1))/2;
5176efdda5ae Initial work on VDP emulation
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140 }
5176efdda5ae Initial work on VDP emulation
Michael Pavone <pavone@retrodev.com>
parents:
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141 }
5176efdda5ae Initial work on VDP emulation
Michael Pavone <pavone@retrodev.com>
parents:
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142
5176efdda5ae Initial work on VDP emulation
Michael Pavone <pavone@retrodev.com>
parents:
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143 void vdp_write_data(vdp *context, uint16_t value)
5176efdda5ae Initial work on VDP emulation
Michael Pavone <pavone@retrodev.com>
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144 {
5176efdda5ae Initial work on VDP emulation
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parents:
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145 context->fifo = value;
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146 context->status |= VDP_STATUS_FIFO;
5176efdda5ae Initial work on VDP emulation
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147 }
19
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
diff changeset
148
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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149 void vdp_write_hscroll(vdp *context, uint16_t value)
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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150 {
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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151 context->hscroll = value & 0x1FF;
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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152 if (value & 0x8000) {
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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153 context->status |= VDP_STATUS_ENABLED;
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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154 } else {
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
diff changeset
155 context->status &= ~VDP_STATUS_ENABLED;
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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156 }
04fc17376999 Sort of working tile rendering and tile test ROM
Michael Pavone <pavone@retrodev.com>
parents: 11
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157 }