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Motorola MEK6800D2 Microcomputer

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  Motorola MEK6800D2 Microcomputer by Bill Degnan - 01/05/2005 17:57
1-10-05

Pictures
http://www.vintagecomputer.net/motorola/mek6800d2/

I have not yet tested this single board computer. I have the manual, it's very good,
should be fun. Requires a 5V DC @ 2.5 MA. I have to splice up an adapter, etc.


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  MEK6800D2 by Bill Degnan - 07/16/2012 19:38
Motorola MEK6800D2
The Motorola MEK6800D2 6802 (6800) processor-based development kit from 1976. The original configuration included a 1K ROM monitor called JBUG, and a 6850 ACIA to drive a teletype or serial device. The original system shipped with 512 bytes of RAM (less than 1K). Click image for larger view.


Motorola MEK6800D2 RAM Upgrade
The previous owner of this computer upgraded the RAM to 32K. You can see by this picture that numerous jumper changes were made. If you review the detailed photos you'll see that many chips were replaced as there are chips with late 70's and even early 1980's date codes. Click image for larger view.


Motorola MEK6800D2 JBUG relocated to F000
A search of the memory map reveals that the JBUG monitor program is present at BOTH E000 and F000, but why? My guess is that the owner was trying to move the monitor to make room for another ROM to be located on E000, but did not finish the job, or changed his mind.


This was the system I took to HOPE 9 to exhibit as part of the M.A.R.C.H. club's booth. The theme was single board computers and trainers. I first got this MEK6800D2 years ago, well before 2005 when I started this web site. I used my time at HOPE as an excuse to finally to debug the entire system, run though the key chip pins with an oscilloscope, test the RAM and so on. I was surprised to find that it had so much RAM. This system has a cassette port and it would probably not be much work to install MIKIBUG and configure to run with a teletype for I/O, or a glass terminal. Given the upgrades, this MEK has more power than my SWTPC 6800.

More Pictures

MEK6800D2 Manual

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  Motorola 6800 JBUG Monitor by Bill Degnan - 04/25/2013 00:01
Message from Roberto Berner:

>Comments: The monitor ROM has 1K extention, and the memory map decoder
>line selects an 8K block, so the JBUG monitor "mirrors" 8 times across
>that 8K block boundaries. You will find the same memory contents in
>$E000 , $E400 , $E800 , $EC00 , $EF00 , $F000 ... etc. I have learned
>almost everything I know with this excellent tool. Greetings from
>Buenos Aires, Argentina.


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