| 1 | ; File name : DisplayPage.asm
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| 2 | ; Project name : Assembly Library
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| 3 | ; Created date : 26.6.2010
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| 4 | ; Last update : 3.7.2010
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| 5 | ; Author : Tomi Tilli
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| 6 | ; Description : Functions for managing display page.
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| 7 |
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| 8 | ; Section containing code
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| 9 | SECTION .text
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| 10 |
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| 11 | ;--------------------------------------------------------------------
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| 12 | ; DisplayPage_SetFromAL
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| 13 | ; Parameters:
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| 14 | ; AL: New display page
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| 15 | ; DS: BDA segment (zero)
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| 16 | ; Returns:
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| 17 | ; Nothing
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| 18 | ; Corrupts registers:
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| 19 | ; AX, DX
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| 20 | ;--------------------------------------------------------------------
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| 21 | ALIGN JUMP_ALIGN
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| 22 | DisplayPage_SetFromAL:
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| 23 | xor ah, ah
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| 24 | mul WORD [VIDEO_BDA.wBytesPerPage] ; AX = Offset to page
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| 25 | mov [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition], ax
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| 26 | ret
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| 27 |
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| 28 |
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| 29 | ;--------------------------------------------------------------------
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| 30 | ; DisplayPage_GetColumnsToALandRowsToAH
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| 31 | ; Parameters:
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| 32 | ; DS: BDA segment (zero)
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| 33 | ; Returns:
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| 34 | ; AL: Number of columns in selected text mode
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| 35 | ; AH: Number of rows in selected text mode
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| 36 | ; Corrupts registers:
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| 37 | ; Nothing
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| 38 | ;--------------------------------------------------------------------
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| 39 | ALIGN JUMP_ALIGN
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| 40 | DisplayPage_GetColumnsToALandRowsToAH:
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| 41 | mov al, [VIDEO_BDA.wColumns] ; 40 or 80
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| 42 | mov ah, 25 ; Always 25 rows on standard text modes
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| 43 | ret
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| 44 |
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| 45 |
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| 46 | ;--------------------------------------------------------------------
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| 47 | ; DisplayPage_SynchronizeToHardware
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| 48 | ; Parameters:
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| 49 | ; DS: BDA segment (zero)
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| 50 | ; Returns:
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| 51 | ; Nothing
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| 52 | ; Corrupts registers:
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| 53 | ; AX, DX
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| 54 | ;--------------------------------------------------------------------
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| 55 | ALIGN JUMP_ALIGN
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| 56 | DisplayPage_SynchronizeToHardware:
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| 57 | xor dx, dx
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| 58 | mov ax, [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition]
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| 59 | div WORD [VIDEO_BDA.wBytesPerPage] ; AX = Page
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| 60 |
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| 61 | cmp al, [VIDEO_BDA.bActivePage]
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| 62 | je SHORT .Return ; Same page, no need to synchronize
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| 63 | mov ah, SELECT_ACTIVE_DISPLAY_PAGE
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| 64 | int BIOS_VIDEO_INTERRUPT_10h
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| 65 | ALIGN JUMP_ALIGN, ret
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| 66 | .Return:
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| 67 | ret
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