1 | ; Project name : Assembly Library |
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2 | ; Description : Functions for preventing CGA snow. |
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3 | |
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4 | ; |
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5 | ; XTIDE Universal BIOS and Associated Tools |
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6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team. |
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7 | ; |
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8 | ; This program is free software; you can redistribute it and/or modify |
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9 | ; it under the terms of the GNU General Public License as published by |
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10 | ; the Free Software Foundation; either version 2 of the License, or |
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11 | ; (at your option) any later version. |
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12 | ; |
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13 | ; This program is distributed in the hope that it will be useful, |
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14 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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16 | ; GNU General Public License for more details. |
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17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html |
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18 | ; |
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19 | |
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20 | ; Section containing code |
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21 | SECTION .text |
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22 | |
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23 | ;-------------------------------------------------------------------- |
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24 | ; CgaSnow_IsCgaPresent |
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25 | ; Parameters: |
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26 | ; DS: BDA segment (zero) |
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27 | ; Returns: |
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28 | ; CF: Set if CGA detected |
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29 | ; Cleared if CGA not detected |
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30 | ; Corrupts registers: |
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31 | ; AX |
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32 | ;-------------------------------------------------------------------- |
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33 | ALIGN DISPLAY_JUMP_ALIGN |
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34 | CgaSnow_IsCgaPresent: |
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35 | cmp WORD [BDA.wVidPort], CGA_STATUS_REGISTER - OFFSET_TO_CGA_STATUS_REGISTER |
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36 | jne SHORT .CgaNotFound |
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37 | |
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38 | ; All standard CGA modes use 25 rows but only EGA and later store it to BDA. |
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39 | cmp BYTE [BDA.bVidRows], 25 |
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40 | jge SHORT .CgaNotFound |
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41 | stc |
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42 | ret |
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43 | ALIGN DISPLAY_JUMP_ALIGN |
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44 | .CgaNotFound: |
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45 | clc |
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46 | ret |
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47 | |
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48 | |
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49 | ; CGA snow prevention must be kept optional to avoid unnecessary |
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50 | ; overhead when building programs meant for non-CGA systems. |
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51 | %ifdef ELIMINATE_CGA_SNOW |
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52 | |
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53 | ;-------------------------------------------------------------------- |
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54 | ; CgaSnow_Stosb |
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55 | ; CgaSnow_Stosw |
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56 | ; Parameters: |
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57 | ; AL: Character to output |
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58 | ; AH: Attribute to output (CgaSnow_StoswWithoutCgaSnow only) |
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59 | ; DS: BDA segment (zero) |
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60 | ; ES:DI: Ptr to video memory where to output |
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61 | ; Returns: |
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62 | ; DI: Incremented for next character |
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63 | ; Corrupts registers: |
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64 | ; AX, DX |
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65 | ;-------------------------------------------------------------------- |
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66 | ALIGN DISPLAY_JUMP_ALIGN |
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67 | CgaSnow_Stosb: |
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68 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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69 | jz SHORT .StosbWithoutWaitSinceUnknownPort |
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70 | |
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71 | mov ah, al |
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72 | cli ; Interrupt request would mess up timing |
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73 | WAIT_UNTIL_SAFE_CGA_WRITE |
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74 | mov al, ah |
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75 | .StosbWithoutWaitSinceUnknownPort: |
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76 | stosb |
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77 | sti |
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78 | ret |
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79 | |
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80 | ALIGN DISPLAY_JUMP_ALIGN |
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81 | CgaSnow_Stosw: |
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82 | push bx |
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83 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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84 | jz SHORT .StoswWithoutWaitSinceUnknownPort |
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85 | |
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86 | xchg bx, ax |
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87 | cli ; Interrupt request would mess up timing |
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88 | WAIT_UNTIL_SAFE_CGA_WRITE |
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89 | xchg ax, bx |
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90 | .StoswWithoutWaitSinceUnknownPort: |
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91 | stosw |
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92 | sti |
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93 | pop bx |
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94 | ret |
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95 | |
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96 | |
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97 | ;-------------------------------------------------------------------- |
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98 | ; CgaSnow_RepMovsb |
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99 | ; Parameters: |
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100 | ; CX: Number of characters to copy |
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101 | ; DS: BDA segment (zero) |
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102 | ; ES:SI: Ptr to video memory where to read from |
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103 | ; ES:DI: Ptr to video memory where to write to |
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104 | ; Returns: |
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105 | ; SI, DI: Updated for next character |
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106 | ; Corrupts registers: |
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107 | ; AX, CX, DX |
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108 | ;-------------------------------------------------------------------- |
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109 | %ifdef EXCLUDE_FROM_XTIDE_UNIVERSAL_BIOS |
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110 | %ifdef MODULE_STRINGS_COMPRESSED |
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111 | %define EXCLUDE |
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112 | %endif |
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113 | %ifdef MODULE_BOOT_MENU |
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114 | %undef EXCLUDE |
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115 | %endif |
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116 | %endif |
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117 | |
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118 | %ifndef EXCLUDE |
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119 | ALIGN DISPLAY_JUMP_ALIGN |
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120 | CgaSnow_RepMovsb: |
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121 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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122 | jz SHORT .RepMovsbWithoutWaitSinceUnknownPort |
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123 | |
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124 | .MovsbNextByte: |
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125 | cli ; Interrupt request would mess up timing |
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126 | WAIT_UNTIL_SAFE_CGA_WRITE |
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127 | es movsb |
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128 | sti |
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129 | loop .MovsbNextByte |
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130 | ret |
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131 | .RepMovsbWithoutWaitSinceUnknownPort: |
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132 | eSEG_STR rep, es, movsb |
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133 | ret |
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134 | %endif |
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135 | %undef EXCLUDE |
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136 | |
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137 | |
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138 | ;-------------------------------------------------------------------- |
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139 | ; LoadCgaStatusRegisterAddressToDXifCgaPresent |
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140 | ; Parameters: |
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141 | ; DS: BDA segment (zero) |
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142 | ; Returns: |
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143 | ; DX: CGA Status Register Address |
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144 | ; ZF: Set if CGA not present |
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145 | ; Cleared if CGA present |
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146 | ; Corrupts registers: |
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147 | ; Nothing |
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148 | ;-------------------------------------------------------------------- |
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149 | ALIGN DISPLAY_JUMP_ALIGN |
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150 | LoadCgaStatusRegisterAddressToDXifCgaPresent: |
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151 | test BYTE [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.bFlags], FLG_CONTEXT_CGA |
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152 | jz SHORT .NoCgaDetected |
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153 | mov dx, CGA_STATUS_REGISTER |
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154 | ALIGN DISPLAY_JUMP_ALIGN, ret |
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155 | .NoCgaDetected: |
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156 | ret |
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157 | |
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158 | |
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159 | %endif ; ELIMINATE_CGA_SNOW |
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