source: buchla-68k/orig/IOLIB/VCLRAV.S@ d21fc6f

Last change on this file since d21fc6f was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 8 years ago

Imported original source code.
  • Property mode set to 100755
File size: 1.6 KB
RevLine 
[3ae31e9]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 .equ 8
19P_ROW .equ 12
20P_COL .equ 14
21P_ATR .equ 16
22P_LEN .equ 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 #$FFFFFFFE,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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