[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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| 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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[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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| 31 | ; AX |
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| 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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| 39 | cmp BYTE [BDA.bVidRows], 25 |
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| 40 | jge SHORT .CgaNotFound |
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[50] | 41 | stc |
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| 42 | ret |
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[369] | 43 | ALIGN DISPLAY_JUMP_ALIGN |
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[50] | 44 | .CgaNotFound: |
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| 45 | clc |
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| 46 | ret |
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[48] | 47 | |
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[50] | 48 | |
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[162] | 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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[48] | 51 | %ifdef ELIMINATE_CGA_SNOW |
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| 52 | |
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| 53 | ;-------------------------------------------------------------------- |
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[49] | 54 | ; CgaSnow_Stosb |
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| 55 | ; CgaSnow_Stosw |
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[48] | 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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[369] | 66 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 67 | CgaSnow_Stosb: |
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[50] | 68 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 69 | jz SHORT .StosbWithoutWaitSinceUnknownPort |
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[48] | 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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[369] | 80 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 81 | CgaSnow_Stosw: |
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[48] | 82 | push bx |
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[50] | 83 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 84 | jz SHORT .StoswWithoutWaitSinceUnknownPort |
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[48] | 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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[162] | 92 | sti |
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[48] | 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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[49] | 98 | ; CgaSnow_RepMovsb |
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[48] | 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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[369] | 109 | ALIGN DISPLAY_JUMP_ALIGN |
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[49] | 110 | CgaSnow_RepMovsb: |
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[50] | 111 | call LoadCgaStatusRegisterAddressToDXifCgaPresent |
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| 112 | jz SHORT .RepMovsbWithoutWaitSinceUnknownPort |
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[48] | 113 | |
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| 114 | .MovsbNextByte: |
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| 115 | cli ; Interrupt request would mess up timing |
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| 116 | WAIT_UNTIL_SAFE_CGA_WRITE |
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[223] | 117 | es movsb |
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[48] | 118 | sti |
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| 119 | loop .MovsbNextByte |
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| 120 | ret |
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| 121 | .RepMovsbWithoutWaitSinceUnknownPort: |
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| 122 | eSEG_STR rep, es, movsb |
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| 123 | ret |
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| 124 | |
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| 125 | |
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| 126 | ;-------------------------------------------------------------------- |
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[50] | 127 | ; LoadCgaStatusRegisterAddressToDXifCgaPresent |
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[48] | 128 | ; Parameters: |
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| 129 | ; DS: BDA segment (zero) |
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| 130 | ; Returns: |
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| 131 | ; DX: CGA Status Register Address |
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[50] | 132 | ; ZF: Set if CGA not present |
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| 133 | ; Cleared if CGA present |
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[48] | 134 | ; Corrupts registers: |
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| 135 | ; Nothing |
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| 136 | ;-------------------------------------------------------------------- |
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[369] | 137 | ALIGN DISPLAY_JUMP_ALIGN |
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[50] | 138 | LoadCgaStatusRegisterAddressToDXifCgaPresent: |
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| 139 | test BYTE [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.bFlags], FLG_CONTEXT_CGA |
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| 140 | jz SHORT .NoCgaDetected |
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| 141 | mov dx, CGA_STATUS_REGISTER |
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[369] | 142 | ALIGN DISPLAY_JUMP_ALIGN, ret |
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[50] | 143 | .NoCgaDetected: |
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[48] | 144 | ret |
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| 145 | |
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| 146 | |
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| 147 | %endif ; ELIMINATE_CGA_SNOW |
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