source: buchla-68k/vlib/vclrav.s@ d10dbee

Last change on this file since d10dbee was 4f508e6, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Converted assembly language files.
  • Property mode set to 100644
File size: 1.5 KB
Line 
1| ------------------------------------------------------------------------------
2| vclrav.s -- clear a character's attributes in video RAM
3| Version 1 -- 1988-10-11 -- D.N. Lynx Crowe
4| (c) Copyright 1988 -- D.N. Lynx Crowe
5| ------------------------------------------------------------------------------
6
7| vclrav(adr, row, col, atr, len)
8| unsigned int |adr, row, col, atr, len;
9
10| Clears attribute 'atr' at ('row', 'col') in the
11| full attribute text object at 'adr'
12| using a line length of 'len'.
13| ------------------------------------------------------------------------------
14 .text
15
16 .xdef _vclrav
17
18P_ADR = 8
19P_ROW = 12
20P_COL = 14
21P_ATR = 16
22P_LEN = 18
23
24_vclrav: link a6,#0 | Link stack frame pointer
25 move.w P_ROW(a6),d0 | Get row
26 mulu P_LEN(a6),d0 | Multiply by len
27 clr.l d1 | Clear out d1
28 move.w P_COL(a6),d1 | Get col
29 add.l d1,d0 | Add col into d0 to get char. #
30 move.l d0,d1 | Develop cw = (cn/2)|6 in d1
31 andi.l #0xFFFFFFFE,d1 | ...
32 move.l d1,d2 | ...
33 add.l d1,d1 | ...
34 add.l d2,d1 | ...
35 add.l P_ADR(a6),d1 | Add sbase to cw
36 movea.l d1,a0 | a0 points at the word with the char.
37 btst.l #0,d0 | Odd char. location ?
38 bne vclrav1 | Jump if so
39
40 addq.l #2,a0 | Point at the attribute word
41 bra vclravx | Go set attribute
42
43vclrav1: addq.l #4,a0 | Point at the attribute word
44
45vclravx: move.w P_ATR(a6),d0 | Get attribute mask
46 not.w d0 | Complement the mask
47 and.w d0,(a0) | Clear attributes in video RAM
48 unlk a6 | Unlink the stack frame
49 rts | Return to caller
50
51 .end
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