Electron 64k mode

discuss both original and modern hardware for the bbc micro/electron
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Yrrah2
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Electron 64k mode

Post by Yrrah2 » Fri Feb 09, 2007 9:56 pm

Hi All,

Al little question I have about the 64k mode.
When I have saved a screen mode 1 (*save screen 3000 8000 if i'm correct) in normal electron mode i can see it again when I type *load screen 3000.
But 64k Mode it is not at 3000 anymore.
I remember that something has changed in this. (I thought my old electron 64k had the same thing)
But I do not know the new starting screen address.

Does somebody know in here?

Cheers

Koen

Fraser
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Post by Fraser » Sat Feb 10, 2007 2:12 pm

Have you looked at the master ram board manual? The screen memory is not directly accessible when there is 32k for programs.

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Yrrah2
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Post by Yrrah2 » Sat Feb 10, 2007 5:24 pm

I have read the manual.
But it is not quite clear to me anymore if it is possible to load pictures with the *load command or not.

I thought this was possible, but I do not know the screen address.
Or is there no screen address anymore in 64 k mode?

I do think there must be, because i can stil draw lines with move and draw if I want to. So there must be a screen address,

Or am I totally wrong.

Cheers

Koen

Fraser
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Post by Fraser » Sat Feb 10, 2007 6:00 pm

The screen memory is not in the addressable memory. The rom is patched to allow the Electron to appear to work as normal. There must be a way to access the screen memory in an unusual way.

g7jjf
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Post by g7jjf » Sat Feb 10, 2007 8:09 pm

To access the screen memory in the original Electron memory map, you have to call an OS routine (as described in the Slogger Manual). The screen memory is not directly accessible in 64K mode so you cannot *LOAD to it.

The following program will load a picture in 64K mode and transfer it across to the original memory to display it on screen.

Code: Select all

   10DIM M% 100
   20FORA%=0TO3
   30P%=M%
   40[OPT A%
   50.go
   60LDA#0:STA&70
   70LDA#&30:STA&71
   80.loop
   90LDY#0:LDA(&70),Y
  100LDY&71:LDX&70
  110BIT exit
  120JSR&FBFD
  130INC&70:BNE loop
  140INC&71:LDA&71:CMP#&80
  150BNE loop
  160.exit
  170RTS
  180]
  190NEXT
  200MODE 1
  210*LOAD PICTURE 3000
  220CALLgo
Jon.

Fraser
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Post by Fraser » Sun Feb 11, 2007 3:08 pm

Is your Master Ram Board manual a paper one or a document from a site?

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Yrrah2
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Post by Yrrah2 » Sun Feb 11, 2007 4:59 pm

I have one one paper. (somewhere in a box, just moved from on place to a new one)
And I have read the on-line version.
Is there a difference?

The great util from Jon solved the problem for me.
Great!

Cheers

Koen

Fraser
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Post by Fraser » Fri Feb 16, 2007 11:53 am

Is there many programs that the MBRs use of D6, D7 and D8 present a problem?

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