[48] | 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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[376] | 4 | ; |
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[491] | 5 | ; XTIDE Universal BIOS and Associated Tools |
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[526] | 6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team. |
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[376] | 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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[491] | 12 | ; |
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[376] | 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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[491] | 16 | ; GNU General Public License for more details. |
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[376] | 17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html |
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[491] | 18 | ; |
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[376] | 19 | |
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[48] | 20 | ; Section containing code |
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| 21 | SECTION .text |
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| 22 | |
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[50] | 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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[583] | 31 | ; Nothing |
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[50] | 32 | ;-------------------------------------------------------------------- |
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[369] | 33 | ALIGN DISPLAY_JUMP_ALIGN |
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[50] | 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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[52] | 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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[593] | 39 | cmp BYTE [BDA.bVidRows], 24 ; BDA contains rows - 1 |
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[583] | 40 | jae SHORT .CgaNotFound |
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[50] | 41 | ret |
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[369] | 42 | ALIGN DISPLAY_JUMP_ALIGN |
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[50] | 43 | .CgaNotFound: |
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| 44 | clc |
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| 45 | ret |
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[48] | 46 | |
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[50] | 47 | |
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[162] | 48 | ; CGA snow prevention must be kept optional to avoid unnecessary |
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| 49 | ; overhead when building programs meant for non-CGA systems. |
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[48] | 50 | %ifdef ELIMINATE_CGA_SNOW |
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| 51 | |
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| 52 | ;-------------------------------------------------------------------- |
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[49] | 53 | ; CgaSnow_Stosb |
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| 54 | ; CgaSnow_Stosw |
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[48] | 55 | ; Parameters: |
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| 56 | ; AL: Character to output |
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| 57 | ; AH: Attribute to output (CgaSnow_StoswWithoutCgaSnow only) |
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| 58 | ; DS: BDA segment (zero) |
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| 59 | ; ES:DI: Ptr to video memory where to output |
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| 60 | ; Returns: |
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| 61 | ; DI: Incremented for next character |
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| 62 | ; Corrupts registers: |
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| 63 | ; AX, DX |
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| 64 | ;-------------------------------------------------------------------- |
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[369] | 65 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 66 | CgaSnow_Stosb: |
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[50] | 67 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 68 | jz SHORT .StosbWithoutWaitSinceUnknownPort |
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[48] | 69 | |
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| 70 | mov ah, al |
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| 71 | cli ; Interrupt request would mess up timing |
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| 72 | WAIT_UNTIL_SAFE_CGA_WRITE |
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| 73 | mov al, ah |
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| 74 | .StosbWithoutWaitSinceUnknownPort: |
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| 75 | stosb |
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| 76 | sti |
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| 77 | ret |
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| 78 | |
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[369] | 79 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 80 | CgaSnow_Stosw: |
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[48] | 81 | push bx |
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[50] | 82 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 83 | jz SHORT .StoswWithoutWaitSinceUnknownPort |
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[48] | 84 | |
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| 85 | xchg bx, ax |
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| 86 | cli ; Interrupt request would mess up timing |
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| 87 | WAIT_UNTIL_SAFE_CGA_WRITE |
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| 88 | xchg ax, bx |
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| 89 | .StoswWithoutWaitSinceUnknownPort: |
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| 90 | stosw |
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[162] | 91 | sti |
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[48] | 92 | pop bx |
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| 93 | ret |
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| 94 | |
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[491] | 95 | |
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[48] | 96 | ;-------------------------------------------------------------------- |
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[49] | 97 | ; CgaSnow_RepMovsb |
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[48] | 98 | ; Parameters: |
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| 99 | ; CX: Number of characters to copy |
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| 100 | ; DS: BDA segment (zero) |
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| 101 | ; ES:SI: Ptr to video memory where to read from |
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| 102 | ; ES:DI: Ptr to video memory where to write to |
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| 103 | ; Returns: |
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| 104 | ; SI, DI: Updated for next character |
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| 105 | ; Corrupts registers: |
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| 106 | ; AX, CX, DX |
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| 107 | ;-------------------------------------------------------------------- |
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[592] | 108 | %ifdef EXCLUDE_FROM_XUB |
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[491] | 109 | %ifdef MODULE_STRINGS_COMPRESSED |
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| 110 | %define EXCLUDE |
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| 111 | %endif |
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| 112 | %ifdef MODULE_BOOT_MENU |
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| 113 | %undef EXCLUDE |
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| 114 | %endif |
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| 115 | %endif |
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| 116 | |
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| 117 | %ifndef EXCLUDE |
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[369] | 118 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 119 | CgaSnow_RepMovsb: |
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[50] | 120 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 121 | jz SHORT .RepMovsbWithoutWaitSinceUnknownPort |
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[48] | 122 | |
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| 123 | .MovsbNextByte: |
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| 124 | cli ; Interrupt request would mess up timing |
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| 125 | WAIT_UNTIL_SAFE_CGA_WRITE |
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[223] | 126 | es movsb |
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[48] | 127 | sti |
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| 128 | loop .MovsbNextByte |
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| 129 | ret |
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| 130 | .RepMovsbWithoutWaitSinceUnknownPort: |
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| 131 | eSEG_STR rep, es, movsb |
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| 132 | ret |
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[489] | 133 | %endif |
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[491] | 134 | %undef EXCLUDE |
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[48] | 135 | |
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[491] | 136 | |
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[48] | 137 | ;-------------------------------------------------------------------- |
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[50] | 138 | ; LoadCgaStatusRegisterAddressToDXifCgaPresent |
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[48] | 139 | ; Parameters: |
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| 140 | ; DS: BDA segment (zero) |
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| 141 | ; Returns: |
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| 142 | ; DX: CGA Status Register Address |
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[50] | 143 | ; ZF: Set if CGA not present |
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| 144 | ; Cleared if CGA present |
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[48] | 145 | ; Corrupts registers: |
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| 146 | ; Nothing |
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| 147 | ;-------------------------------------------------------------------- |
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[369] | 148 | ALIGN DISPLAY_JUMP_ALIGN |
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[50] | 149 | LoadCgaStatusRegisterAddressToDXifCgaPresent: |
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| 150 | test BYTE [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.bFlags], FLG_CONTEXT_CGA |
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| 151 | jz SHORT .NoCgaDetected |
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| 152 | mov dx, CGA_STATUS_REGISTER |
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[369] | 153 | ALIGN DISPLAY_JUMP_ALIGN, ret |
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[50] | 154 | .NoCgaDetected: |
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[48] | 155 | ret |
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| 156 | |
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| 157 | |
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| 158 | %endif ; ELIMINATE_CGA_SNOW |
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