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tane

Garbage characters in transition

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Posted (edited)

I thought it was just to scan the memory and find the characters, and then replace them by zeros, but is not that easy.

 

How can be fixed a transition between 2 programs?  It's shown around 0.1 seconds, but the screen should be black without any character.

 

bug1.jpg.71405fa127df5ce2c870cee9b5039985.jpg

 

The characters are located in memory around $2000 and $2600. The strange thing is if the characters are located let's say between $21a0-$22a0, and then they are replaced by zeros before to enter in the transition, then unexpectedly the screen shows the next set of characters of $2500-$2600.

 

Edited by tane

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19 minutes ago, globe said:

For simple fix you could set color registers (708-712) to zero.

Tested but it didn't work.

  lda #$00
  sta $02c4
  sta $02c5
  sta $02c6
  sta $02c7
  sta $02c8

 

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Do you load the 2nd program from an IO device (e.g. disk?). 
This will disable parts of the VBI which read the shadow registers.

You have to wait one frame after setting the shadows before you continue.

 

lda #$00
  sta $02c4
  sta $02c5
  sta $02c6
  sta $02c7
  sta $02c8

lda $14

wait:

cmp $14

beq wait

 

 

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2 hours ago, JAC! said:

Do you load the 2nd program from an IO device (e.g. disk?). 

No, just a different segment.

P.M. sent.

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Easy solution would be just blank the screen then re-enable once the next segment has loaded.

Or have some sort of interim loading screen.

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9 hours ago, Rybags said:

Easy solution would be just blank the screen then re-enable once the next segment has loaded.

Almost. Problem solved: to delay a "cli" makes the trick.

 

16 hours ago, JAC! said:

Do you load the 2nd program from an IO device (e.g. disk?).

Still I don't have a SIO device, but already in the way.

 

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On 8/1/2021 at 5:16 AM, tane said:

No, just a different segment.

P.M. sent.

In fact that is loading from an IO device. Control returns to DOS at the RTS of the first segment and DOS blocks NMI 2nd stage via SEI and IRQ. That's why CLI solves the problem.

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