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