| [4f508e6] | 1 | | ------------------------------------------------------------------------------
|
|---|
| 2 | | glcplot.s -- plot a pixel on the LCD display
|
|---|
| 3 | | Version 2 -- 1987-04-23 -- D.N. Lynx Crowe
|
|---|
| 4 | | (c) Copyright 1987 -- D.N. Lynx Crowe
|
|---|
| 5 |
|
|---|
| 6 | | GLCplot(x, y, val)
|
|---|
| 7 | | unsigned x, y, val);
|
|---|
| 8 |
|
|---|
| 9 | | Plot a pixel at ('x', 'y') using lcdbase as the plane address
|
|---|
| 10 | | in GLC RAM. If 'val' is zero, the pixel is cleared,
|
|---|
| 11 | | otherwise the pixel is cleared. No error checking is done.
|
|---|
| 12 | | Limits: 0 LE x LE 511, 0 LE y LE 63.
|
|---|
| 13 | | ------------------------------------------------------------------------------
|
|---|
| [f40a309] | 14 | .text
|
|---|
| [4f508e6] | 15 |
|
|---|
| [f40a309] | 16 | .xdef _GLCplot
|
|---|
| 17 | .xref _lcd_a0,_lcd_a1,_lcdbase
|
|---|
| [4f508e6] | 18 |
|
|---|
| 19 | XLOC = 8 | 'x' parameter offset
|
|---|
| 20 | YLOC = 10 | 'y' parameter offset
|
|---|
| 21 | VAL = 12 | 'val' parameter offset
|
|---|
| 22 |
|
|---|
| 23 | G_CRSWR = 0x46 | GLC set cursor command
|
|---|
| 24 | G_MWRITE = 0x42 | GLC write command
|
|---|
| 25 | G_MREAD = 0x43 | GLC read command
|
|---|
| 26 |
|
|---|
| [f40a309] | 27 | .page
|
|---|
| [4f508e6] | 28 |
|
|---|
| 29 | _GLCplot: link a6,#0 | Link stack frames
|
|---|
| 30 | moveq #63,d0 | d0 = (63-y) | 85
|
|---|
| 31 | sub.w YLOC(a6),d0 | ...
|
|---|
| 32 | mulu #85,d0 | ...
|
|---|
| 33 | clr.l d1 | d1 = x/6
|
|---|
| 34 | move.w XLOC(a6),d1 | ...
|
|---|
| 35 | divu #6,d1 | ...
|
|---|
| 36 | add.w d1,d0 | d0 = (63-y)|85 + (x/6)
|
|---|
| 37 | swap d1 | d2 = 7 - (x%6) % 8
|
|---|
| 38 | moveq #7,d2 | ...
|
|---|
| 39 | sub.w d1,d2 | ...
|
|---|
| 40 | andi.w #7,d2 | ...
|
|---|
| 41 | lsr.w #3,d1 | d1 = (x%6) / 8
|
|---|
| 42 | add.w d1,d0 | d0 = cursor address
|
|---|
| 43 | add.w _lcdbase,d0 | ...
|
|---|
| 44 | move.w d0,d1 | d1 = cursor address, too
|
|---|
| 45 | move.b #G_CRSWR,_lcd_a1 | Send cursor address to GLC
|
|---|
| 46 | move.b d0,_lcd_a0 | ...
|
|---|
| 47 | lsr.w #8,d0 | ...
|
|---|
| 48 | move.b d0,_lcd_a0 | ...
|
|---|
| 49 | move.b #G_MREAD,_lcd_a1 | Read old pixel byte
|
|---|
| 50 | move.b _lcd_a1,d0 | ... into d0
|
|---|
| 51 | tst.w VAL(a6) | Check val for zero
|
|---|
| 52 | beq glcplt1 | Jump if val EQ 0
|
|---|
| 53 |
|
|---|
| 54 | bset d2,d0 | Set the pixel to 1
|
|---|
| 55 | bra glcplt2 | Go write pixel to GLC
|
|---|
| 56 |
|
|---|
| 57 | glcplt1: bclr d2,d0 | Clear the pixel to 0
|
|---|
| 58 |
|
|---|
| 59 | glcplt2: move.b #G_CRSWR,_lcd_a1 | Send cursor address to GLC
|
|---|
| 60 | move.b d1,_lcd_a0 | ...
|
|---|
| 61 | lsr.w #8,d1 | ...
|
|---|
| 62 | move.b d1,_lcd_a0 | ...
|
|---|
| 63 | move.b #G_MWRITE,_lcd_a1 | Setup GLC to write pixel
|
|---|
| 64 | move.b d0,_lcd_a0 | Write pixel
|
|---|
| 65 | unlk a6 | Unlink stack frames
|
|---|
| 66 | rts | Return to caller
|
|---|
| 67 |
|
|---|
| [f40a309] | 68 | .end
|
|---|
![(please configure the [header_logo] section in trac.ini)](http://bob.lopatic.de/chrome/site/logo.png){kind=logo}
