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Forums > C64 Coding > Left/Right Border switching in middle of rasterline
2016-10-22 19:58
Monte Carlos

Registered: Jun 2004
Posts: 359
Left/Right Border switching in middle of rasterline

The last days i experimented a little with bit 3 of $d016. I had the brainfart to broaden the border on the left and keep it normal on the right. Disappointingly, this seems to work only in every non badline. If i try to switch bit 3 of $d016 during a badline i either get both left and right borders equal or i turn off the border completely for the next rasterline. Does somebody have an explanation in terms of internal VIC timing? I also tried modifying the timing with sprites or HSP to be able to write to $d016 in the correct cycle.
 
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2016-10-25 19:38
Rastah Bar
Account closed

Registered: Oct 2012
Posts: 336
Cool. The idle byte seems to be shifted down by 1 line. Where does it get its color from?

Can't you hide it by making the right border broad instead?
2016-10-25 19:55
Monte Carlos

Registered: Jun 2004
Posts: 359
From the lo nibble of the opcode following the st? $d011 (?=a|x|y).
2016-10-25 20:43
Rastah Bar
Account closed

Registered: Oct 2012
Posts: 336
Quoting Color Bar
Can't you hide it by making the right border broad instead?

I guess that's not very handy for a text scroller.
2016-10-26 10:07
Monte Carlos

Registered: Jun 2004
Posts: 359
Not even in arabic language, because a major bug would appear on the left side independent on scroll direction.
2017-06-04 19:29
Digger

Registered: Mar 2005
Posts: 437
Looks like you've done the impossible MonteCarlos! – changed the color in the middle of the char – second row at the very right ;-D)

I guess one could use bitmap mode without badlines to create 39 column wide scroll using VSP?
2017-06-04 20:48
Monte Carlos

Registered: Jun 2004
Posts: 359
Where do you see a split in the middle of a char?
Did you use VICE or real machine?
I'm not aware of that what you want to tell me at the moment.
2017-06-04 20:51
Digger

Registered: Mar 2005
Posts: 437
@MC: Haha, in your screenshot! Second row, the very last char. I am not sure what's going on there but it looks like you've split the atom ;-)
2017-06-05 05:10
ChristopherJam

Registered: Aug 2004
Posts: 1409
That's a blue $ff character! The split is between char foreground and $d021
2017-06-05 11:11
Oswald

Registered: Apr 2002
Posts: 5094
the latest shape demo uses sprites to achieve a 41 char wide screen for 40 column scroll.
2017-06-05 14:56
Digger

Registered: Mar 2005
Posts: 437
Right Oswald – well spotted!

@CJ: Ah, haha how could I miss that?!
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