1 | | ------------------------------------------------------------------------------
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2 | | vputa.s -- store character attributes in video RAM
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3 | | Version 1 -- 1988-03-14 -- D.N. Lynx Crowe
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4 | | (c) Copyright 1988 -- D.N. Lynx Crowe
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5 | | ------------------------------------------------------------------------------
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6 |
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7 | | vputa(sbase, row, col, attrib)
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8 | | unsigned int *sbase, row, col, attrib;
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9 |
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10 | | Stores attribute value 'attrib' for the character
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11 | | located at ('row','col') in VSDD RAM starting at 'sbase'.
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12 | | Assumes a 64 character line and full character attributes.
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13 | | ------------------------------------------------------------------------------
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14 | .text
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15 |
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16 | .xdef vputa
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17 |
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18 | SBASE = 8 | LONG - 'sbase'
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19 | ROW = 12 | WORD - 'row'
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20 | COL = 14 | WORD - 'col'
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21 | ATTR = 16 | WORD - 'attrib'
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22 |
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23 | vputa: link a6,#0 | Link stack frame pointer
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24 | clr.l d0 | Clear out d0
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25 | move.w ROW(a6),d0 | Get row
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26 | lsl.l #6,d0 | Multiply by 64 (shift left 6)
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27 | move.w COL(a6),d1 | Get col
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28 | andi.l #0x0000003F,d1 | Mask down to 6 bits
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29 | or.l d1,d0 | OR into d0 to get char. #
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30 | move.w d0,d1 | Develop cw = (cn/2)*6 in d1
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31 | andi.l #0xFFFFFFFE,d1 | ...
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32 | move.l d1,d2 | ...
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33 | add.l d1,d1 | ...
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34 | add.l d2,d1 | ...
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35 | add.l SBASE(a6),d1 | Add sbase to cw
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36 | movea.l d1,a0 | a0 points at the word with the char.
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37 | btst.l #0,d0 | Odd char. location ?
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38 | bne vputa1 | Jump if so
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39 |
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40 | move.w ATTR(a6),2(a0) | Store new attribute word in video RAM
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41 |
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42 | vputax: unlk a6 | Unlink the stack frame
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43 | rts | Done -- return to caller
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44 |
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45 | vputa1: move.w ATTR(a6),4(a0) | Store new attribute word in video RAM
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46 | bra vputax | Done -- go return to caller
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47 |
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48 | .end
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