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Dwangi
Registered: Dec 2001
Posts: 129 |
$e544 ?
Hope this is the right forum to put a question..
I have heard so much comments of what is right and wrong when setting up a multicolor screen (so it also work on old c64:s´)
lda color
sta $0286
jsr $e544
thats fuck up on an old c64 ??? |
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Zyron
Registered: Jan 2002
Posts: 2381 |
lda #col
sta $d021
jsr $e536
works on both old & new c64s. ;) |
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lft
Registered: Jul 2007
Posts: 369 |
This behaviour is actually explained in Bagnall's On The Edge. Early revisions of the VIC had a problem where small dots of the foreground colour would flicker randomly all over the screen. Obviously, this would have given potential customers a really bad first impression of the C64. There was no time to fix the hardware, so they added a workaround to the kernal ROM, where the current background colour would be stored into all colour RAM locations corresponding to blank characters on the screen. |
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tlr
Registered: Sep 2003
Posts: 1714 |
Quote: lda #col
sta $d021
jsr $e536
works on both old & new c64s. ;)
$e544 sets color mem to white in kernal rev1... |
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JackAsser
Registered: Jun 2002
Posts: 1989 |
THIRTEEN YEARS BETWEEN TWO POSTS!!!! :D Horray for Zyron - The thread awakener! ***Svindlande*** |
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Stablizer
Registered: Jan 2016
Posts: 19 |
jsr $e544 just clears the screen. :) |
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TheRyk
Registered: Mar 2009
Posts: 2070 |
I find Zyron's hint kinda kewl and helpful to prevent old KERNAL Rev CLRSCR trouble, even after so many years :)
PS: Had funny experiences with this release and an old KERNAL rev compo machine hehehe
DuTreff
on old rev white on white as it uses $E544 CLRSCR |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
A "clean" and portable version would be:
clrscrn
TAX
LDA col2pet,X ; convert color to PETSCII code
JSR $FFD2 ; CHROUT
LDA #$93 ; CLR (PETSCII code)
JMP $FFD2 ; CHROUT
col2pet
.bxte $90,$05,$1C,$9F,$9C,$1E,$1F,$9E
.byte $81,$95,$96,$97,$98,$99,$9A,$9B
The col2pet table is not really required, the same table can be found in Kernal-ROM at adress $E8DA, hence:
col2pet = $E8DA
clrscrn
TAX
LDA col2pet,X ; convert color to PETSCII code
JSR $FFD2 ; CHROUT
LDA #$93 ; CLR (PETSCII code)
JMP $FFD2 ; CHROUT
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Dwangi
Registered: Dec 2001
Posts: 129 |
Hi
Thanks for all the answers.
I never use ROM:s myself. I asked because alot of demos between 1987 and 1992 (and even some games) displayed single colours on an old C64 were it should be multicolours.
I have also seen alot of coders trying to teach other how to do it "right".
For example in this demo.
Lunacy 6 by Antic.
Anyway seems like this topic should have been in the coders section. Sorry for this. |
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JackAsser
Registered: Jun 2002
Posts: 1989 |
Quote: Hi
Thanks for all the answers.
I never use ROM:s myself. I asked because alot of demos between 1987 and 1992 (and even some games) displayed single colours on an old C64 were it should be multicolours.
I have also seen alot of coders trying to teach other how to do it "right".
For example in this demo.
Lunacy 6 by Antic.
Anyway seems like this topic should have been in the coders section. Sorry for this.
<3 |
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Count Zero
Registered: Jan 2003
Posts: 1821 |
Resolved after 18 years I assume. |
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