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Ejner
Registered: Oct 2012
Posts: 43 |
Show Koala Pic
I'm sure noone here has any problems with showing a simple Koala picture, but I came across this piece of code on codebase64.org and wondered why this had to be done so complicated...?
http://codebase64.org/doku.php?id=base:calculate_vic_settings_f..
In TurboAssembler it's pretty simple to calculate the VIC settings, see my example below. Isn't something similar possible with KickAssembler? Just wondering...
Example in TurboAssembler:
;---------------------------------------
; Show Koala
;---------------------------------------
koala = $6000
screen = $5c00
;---------------------------------------
bank = koala/$4000
*= $1000
lda #$3b
sta $d011
lda #koala-($4000*bank)/1024
ora #(screen-($4000*bank))/64
sta $d018
lda #$d8
sta $d016
lda $dd02
ora #%00000011
sta $dd02
lda $dd00
and #%11111100
ora #3-bank
sta $dd00
ldx #0
copy lda koala+$1f40,x
sta screen,x
lda koala+$2040,x
sta screen+$0100,x
lda koala+$2140,x
sta screen+$0200,x
lda koala+$2228,x
sta screen+$02e8,x
lda koala+$2328,x
sta $d800,x
lda koala+$2428,x
sta $d900,x
lda koala+$2528,x
sta $da00,x
lda koala+$2610,x
sta $dae8,x
inx
bne copy
lda koala+$2710
sta $d021
lsr a
lsr a
lsr a
lsr a
sta $d020
lda #0
cmp $0277 ;wait for key
bne *-3
lda $dd02
ora #%00000011
sta $dd02
lda $dd00
and #%11111100
ora #%00000011
sta $dd00
lda #$1b
sta $d011
lda #$15
sta $d018
lda #$c8
sta $d016
jmp $9000
;---------------------------------------
Note: The result of "bank = koala/$4000" is an integer. |
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soci
Registered: Sep 2003
Posts: 480 |
From the calculations above it might not be obvious but the same address lines are wired to the top and bottom nibble of $d018.
Bit 0 could have been used for finer font base address selection in ECM mode, unfortunately that's not how it was implemented.
=8192 bitmap = 8192
=1024 screen = 1024
.block
=$2000 bmpfont .var $0000 | bits(bitmap)
=$0400 screen .var $0000 | bits(screen)
.0000 a9 18 lda #$18 lda #screen[10:14]..bmpfont[10:14]
.0002 8d 18 d0 sta $d018 sta $d018
.0005 ad 00 dd lda $dd00 lda $dd00
and #~(screen[14:16] || [])
.0008 09 03 ora #$03 ora #(~screen)[14:16] || []
.000a 8d 00 dd sta $dd00 sta $dd00
.cerror (screen ^ bmpfont)[14:16], "different bank?!"
.bend
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Ejner
Registered: Oct 2012
Posts: 43 |
Groepaz, soci:
Okay, I didn't know that "|" (ORA?) feature before. I learn something new all the time :-)
koala = $6000
screen = $5c00
*= $1000
lda #[[>screen & $3f] << 2] | [[>koala & $3f] >> 2]
sta $d018
lda $dd00
and #%11111100
ora #3-[>koala >> 6]
sta $dd00
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Oswald
Registered: Apr 2002
Posts: 5094 |
soci, thats a neat idea, tho I cant think of a scenario where it would be useful :) maybe some demo effect with lots of prepped csets. |
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Dr.j
Registered: Feb 2003
Posts: 277 |
Soci , hehe i don't like to kill a fly with RPG but
what do you mean
by:
$0000 | bits(bitmap) where is the bits function? or i miss something.
and later:
and #~(screen[14:16] || []) hehe for not a C coders
could you make a friendly explain ? (you can do it on
private if you prefer) |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
I think Soci is talking about 64tass:
http://tass64.sourceforge.net/ |
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Dr.j
Registered: Feb 2003
Posts: 277 |
oh Flavioweb ok. i am kickass person so i leave it aside
for now hehe |
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soci
Registered: Sep 2003
Posts: 480 |
Too much late coding yesterday ;) It would go even more off topic if I'd go into details in this thread.
The code fragment was only a demonstration about constructing $d018 values without using divisions and shifts.
Normally I use some variant of this:
lda #((font >> 10) & $0f) | ((screen >> 6) & $f0)
sta $d018
lda $dd00
ora #3
eor #font >> 14
sta $dd00 Even if this version is wasting 2 bytes half the time for the $dd00 calculation. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
why not just store a fixed value to $dd00 though? i dare to say that "properly" ORing the value is very rarely needed - certainly almost never in the usual setup code at the start of your intro/demo/whatever :) |
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soci
Registered: Sep 2003
Posts: 480 |
Not sure why. I just checked and even my one filers are mostly doing the masking, where there's no chance of loader interference.
It must be tradition then.
So I now declare trademark rights on the ora/eor version. It may only identify genuine Singular productions ;) |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
i see this often, also with eg $01 or $d011 .... people must have learned it somewhere :) |
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