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 Subject: RE: Bit-3 80 column board for 8-bit
Author: Jason Harmon (
Date:   06-13-2014 21:49

Hi David,

Thanks for your response and I apologize for my delayed response. Would I be correct to assume you are the same guy who among other Atari contributions created Magic Sac and Spectre Mac emulator hardware/software for the ST?

Regarding the 800/Bit-3/ATR-8000 setup I have, this is what I can tell you.

1) The 800 is connected to the ATR-8000 via a normal Atari SIO cable. Two standard 360K floppies are connected to the ATR8000 via a standard floppy ribbon connector.

2) In order to switch to terminal mode, you load an Atari (6502) program called ATMON. This basically loads a driver that turns the 800 into a custom terminal for the ATR8000 and all keyboard input is then sent over the SIO to the ATR8000, and displays the output from the ATR8000 on the 800's display.

3) ATMON appears to have some logic that can detect the presence of the Bit-3 card, and when it is present will enable 80 column mode on the Bit-3. Once enabled, this allows the ATMON terminal running on the 800 to display the serial output from the CP/M apps running on the ATR8000 in 80 column mode.

4) After ATMON is loaded, you can replace the Atari format disk with a CP/M boot disk and issue a command that will cause the ATR8000 to boot CP/M to the "A>" prompt. From that point on the Atari is just a terminal for the ATR-8000.

5) I can certainly get a dis-assembly of the ATMON Atari app since it appears to be just a normal Atari binary.

7) I don't know how to get any of the firmware from the Bit-3 card. All of the software for it appears to be in firmware on the card. It can be enabled by calling a ML subroutine via a USR() from BASIC, and I suspect it overlays some of the OS on the 800 when it initializes, but I don't know for sure.

Most everything works. The main problem I have is that when booting to CP/M on the ATR8000 with the Bit-3's 80 column mode enabled, the screen freezes (does not allow input to the ATR8000 via the keyboard and/or does not display the output on the screen. It works in normal 40 column mode, and the Bit-3 works when not using ATMON/ATR8000 so I have to suspect there is some minor SW issue dealing with IO from the ATR8000->Atari->Bit3 flow.


Jason Harmon

 Topics Author  Date
  Bit3 80 Column Mode with ATR8000 new Jason Harmon 11-07-2013 18:42 
   Bit-3 80 column board for 8-bit new David Small 06-08-2014 03:45 
    RE: Bit-3 80 column board for 8-bit  Jason Harmon 06-13-2014 21:49 
   RE: Bit3 80 Column Mode with ATR8000 new David Small 06-08-2014 04:09 
    RE: Bit3 80 Column Mode with ATR8000 new Ken Barten 05-20-2015 17:33 
     RE: Bit3 80 Column Mode with ATR8000 new Ken Barten 05-20-2015 18:35 
   RE: Bit3 80 Column Mode with ATR8000 new David Small 06-08-2014 04:09 

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