The CPMputer ;-)

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The CPMputer ;-)

Postby no0207 » Oct Sun 06, 2013 5:09 am

Recently I am playing around with a Z180 chip. First wanted to have it execute small pieces of test code to explore its behavior. At the very beginning of these experiments there was the question whether or not to use Eproms to provide program contents to the Z180 system. I did not like the idea at all having to burn another Eprom at each trial-and-error step of development. Thanks to some hints at a microcontroller forum on the web I finally found a nice alternative:

the Zilog has only RAM in its entire address space. An Atmega serves as control processor. Initially it keeps the Z180 in /RESET and allows me to manipulate the RAM through an serial monitor program. When everything is ready, the Atmega disconnects itself from the bus and releases the Z180 who takes over control. In the meantime the concept is evolving more and more towards a computer which can run CP/M. At this moment I am planning to design it on a 160x100mm PCB prototype. Attached are the schematics:

http://hive-project.de/board/download/file.php?id=2486

I am planning to give it a nice housing in an TECO D14:

http://www.reichelt.de/?SID=%20;ARTICLE=21223

However this is a hobby project, so it will take some time until it becomes reality. I would be glad if the hardware is ready by the end of the year.

Stay tuned ;-)
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Re: The CPMputer ;-)

Postby no0207 » Oct Mon 14, 2013 4:37 pm

Today I finalized the layout and ordered a prototype PCB. Now I have to be really patient - it will take 8 working days until I will receive the prototype...

Image
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Re: The CPMputer ;-)

Postby no0207 » Oct Wed 16, 2013 12:39 pm

Today I received a parcel with the casing for my planned do-it yourself computer. But still must wait more than a week for the PCB. In order to make it affordable I always choose the "8 working days delivery option" with my PCB manufacturer. And this gives me a very hard time, each time I order another board. Wish I was a millionaire :P

Could not resist to make at least a check with a 1:1 printout if the board will fit into the box ;)
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Re: The CPMputer ;-)

Postby no0207 » Oct Thu 31, 2013 3:23 am

Finally received the long awaited PCB.
Putting things together was (as always) the easy part - took only two to three hours. But somehow no sign of life came out of the machine. Until I finally realized the /CTS input to the Z180's cereal interface was actually not on low. Had to rearrange things a little bit - and finally a "Hello World!" showed up on the terminal's screen!
That is always a very enjoyable moment - but soon gets boring. Firmware development is time consuming. Fortunately in this particular case I had persuaded Grant Searle to also play a little bit with the Z180 processor one month ago - that guy achieves things within days for which I need months. He had kindly sent me an Z180 adapted version of the Nascom Basic (Microsoft Basic 4.7) some time ago - so now I could give it a try - and it worked out of the box!

Yipiiieee!!!!

Now its my turn - just about to figure out how to implement CP/M 2.2 on this box...

==> to be continued
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