Re: cbm 8032 io area $e800-$e8ff decoding

What's at $E800 - $E80F?

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  ----- Original Message ----- 
  From: Steve Gray 
  To: cbm-hackers@musoftware.de 
  Sent: Wednesday, November 09, 2016 4:38 PM
  Subject: Re: cbm 8032 io area $e800-$e8ff decoding


  Nope, there's no un-allocated space in that range. This has been my problem with my ColourPET project. Firstly, I use a 4K edit rom, which means the area from $E900-EFFF is used for that. Then I want to allocate $8800-8FFF for 80-column colour ram. If you use any option roms then $9xxx and $Axxx are out. That really doesn't leave anywhere in the memory map for anything else.


  So, assuming you dont have a ColourPET board (ha!) YOU could use $8800-$8FFF. It's free. 


  If you are using a 2K Edit ROM you can use $E900-E9FF, however if you have a SuperPET it will use $EFEx-EFFF for it's memory control and ACIA chip.


  What I'm thinking of doing is making a board that mounts on the 6545 CRTC chip socket and intercepts the chip select signal, then runs it through a 3-8 decoder using A1,A2,A3. This will let me use output 0 for the CRTC and then I would have outputs 1-7 for my own use.


  Steve




------------------------------------------------------------------------------
  From: didier derny <didier@aida.org>
  To: cbm-hackers@musoftware.de 
  Sent: Wednesday, November 9, 2016 3:30 PM
  Subject: cbm 8032 io area $e800-$e8ff decoding


  Hi

  Is there any solution to use in area between $e800-$e8ff to add extra 
  chips ?  (PIA / ACIA) ?

  is the decoding partial and standard chips shadowed  or any free places ?

  --
  didier




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