New to the group - My SC126 project

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Nick Tate

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Jul 2, 2021, 11:15:49 AM7/2/21
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Hi everyone,  I'm new to the group and I build Z80 computer projects. I got an SC126 in June 2020 after seeing it on the RC2014 group on Facebook. I'm very pleased with it and i'm very much a fan of Steve Cousins work and the other creators of RC2014 products. Most of the time I use it to run CP/M applications, SuperCalc, WordStar, HItech C compiler and BASIC for coding, and games, etc... 
https://www.flickr.com/photos/nicktate/50152047456/in/dateposted/

I mostly program in machine code/hand assembly on my other Z80 computer projects which are my custom designs based on the Micro Professor. 

I prefer the Hex keyboard and 7 segment LED display to the terminal display of SCMonitor so I designed a special Micro Professor add on for the SC126. 

In Feb 2021 I got thinking about how I was going to do this. I had to learn about the Z180 in depth and the operation of the SC126 circuits. A Facebook user on a Z80 group helped me to understand how the MMU works. I have a previous 24MHz Z80 build I had just finished that used some very fast circuits so I re-used some of those in the new project. I decided to keep the keyboard and LED display the same as all my previous builds too.

After not too long I had the design worked out and ready to start construction... 
All of a sudden I decided to spray paint the Veroboard a dark blue colour before getting the soldering iron out! Gives it nice appearance too! 

The design is made up of new firmware to replace the existing SCMonitor ROM and an interface board containing the high speed logic that plugs in to the RC2014  bus on the SC126 mainboard. A ribbon cable connects this to the keyboard/display unit shown here...

After several weeks I finished the build and started testing. It didn't work entirely first time. I had the MMU banks set up wrong plus an I/O address decoding clash with the CPU I/O registers and a few other small issues I sorted out quickly.
So here is the finished project...

I have further information on this project here, including schematics, a ROM image, photos, its still work in progress.

I will leave this here as its getting long but please feel free to ask any questions if you are interested and thank you for reading.




Justin Skists

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Jul 2, 2021, 12:30:31 PM7/2/21
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I do love the amount of work that you've put into this!

Justin.

Mark T

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Jul 2, 2021, 1:30:57 PM7/2/21
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Very neat and tidy for a point to point wiring build. Do you have any plans to build the keyboard and display into a case or create a pcb version?

Nick Tate

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Jul 2, 2021, 3:04:31 PM7/2/21
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Hi, Thanks! 

Nick Tate

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Jul 2, 2021, 3:11:41 PM7/2/21
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@Mark T,  I don't case up many of my projects because I don't really have the right tools to do a good job and money is tight at the moment.  It might happen one day tho :)

Nick Tate

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Jul 2, 2021, 3:15:41 PM7/2/21
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Hi, Thanks!

On Friday, 2 July 2021 at 17:30:31 UTC+1 j.sk...@gmail.com wrote:

Mark T

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Jul 2, 2021, 4:03:29 PM7/2/21
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I’m the same, I enjoy experimenting with the electronics more than producing a finished product, but the keyboard and display looks like it could be fitted to the top of a case if the dimensions of the pcb were matched to a readily available case.

Nick Tate

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Jul 3, 2021, 3:16:24 AM7/3/21
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@Mark T
I might make one out of cardboard as a mock up first to get the dimensions right. 

Kevin Kozlowski

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Oct 19, 2021, 3:51:02 AM10/19/21
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Very cool Nick.

What type of switches are you using on the keyboard? They appear to be easy to press from your videos and have a nice feedback "click".

-Kevin

Nick Tate

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Oct 19, 2021, 4:59:45 PM10/19/21
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Hi  Kevin Kozlowski
Thanks!   I purchased the switches from here...


Yes they only need light pressure to press and have a slight click,  the dual mic's on my phone are making it seem a bit louder than it really is.  

Nick

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