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RE: 8Bit adder from discrete transistors

Stuart_S — Wed, 05 Nov 2025 20:02:43 GMT

We did this circuit in one of our digital practicals at Uni a while back (that was converted to VHDL), build a half adder and full adder (half adder with carry). Our add with carry features two XOR, two ANDs and an OR -which appears as one of your bit adding modules. Maybe there's an exercise here using De-Morgan's theorem to reduce the chip count.

Half Adder

Full Adder

I've included the truth tables and simulations for reference and support

RE: 8Bit adder from discrete transistors

DAB — Thu, 14 Nov 2024 19:15:57 GMT

One of my first purchases from the surplus market was an old RTL board from some computer, back in the 1960's.

So your going back to that era for a project brought a smile to my face as I remembered the fun I had tracing the circuit from the logic boards.

RE: 8Bit adder from discrete transistors

michaelkellett — Thu, 14 Nov 2024 14:39:38 GMT

Did you consider NOR gates as your basic building block. A single transistor can implement a NOR gate and any other gate may be composed from a combination of NOR gates.

https://en.wikipedia.org/wiki/NOR_gate

https://ecstudiosystems.com/discover/textbooks/basic-electronics/logic-gates/rtl/

https://www.geeksforgeeks.org/implementation-of-full-adder-using-nor-gates/

It wouldn't use any less parts !

( But might be easier to tolerance and understand.)

You can actually squeeze a TO92 transistor of any pin out into a footprint of any layout (50 years of electronics work has offered many opportunities to test this proposition) but it wouldn't look very neat.

RE: The Digilent Arty S7: An Unexpected Journey

Former Member — Tue, 28 May 2024 11:17:41 GMT

When I read:

Step 1 - Clock setup

Add the DDR Clock and System Reset by selecting them from the "Board" tab, right-click on the selected item, and click on "Auto Connect". Customise the Clock block by double-clicking on it, and in Board tab select "Reset" for "EXT_RESET_IN", and

in"Output Clock" tab, select "clock_out2" and set 200MHz as frequency,

then select "Reset Active Low" for Reset Type. Run the Connection Automation wizard, and accept all the defaults.

I dont know what to do!

RE: One of the Best CPU ever made: The CELL processor.

DAB — Tue, 26 Dec 2023 20:02:43 GMT

Yes, it takes more than innovative hardware to make a good product.

Without a well thought out software support solution, many interesting products just fail.

RE: One of the Best CPU ever made: The CELL processor.

maxpowerr — Tue, 26 Dec 2023 13:25:02 GMT

Interesting information. I just don’t understand why the PS3 died a year later.

RE: One of the Best CPU ever made: Sparc Family

DAB — Sat, 23 Dec 2023 19:13:10 GMT

Yes I remember when they were all the rage.

Now only a few of us remember they ever existed.

RE: One of the Best CPU ever made: Sparc Family

shabaz — Thu, 21 Dec 2023 22:46:55 GMT

Amazing machines. Full of neat features like rotating register sets! Also, Sun had one of the best debuggers (DBX) until GNU could reach the point of replacing the Sun compiler tools. Plus Solaris had DTrace. And there were all sorts of sophisticated tools for instrumenting and performance monitoring of C/C++ code, that I have never seen on other platforms since (Android being one of the exceptions).

I still have a Sun Blade 2000 desktop machine (it's massive, you wouldn't want it on top of the desk!), although it's not been powered up in a decade. That beast was 64-bit, and could drive a couple of full-HD monitors (great for software development), when PCs were still running 32-bit Windows, and 1024x768 resolution was considered good.

(image source: Wikimedia Commons)

RE: One of the Best CPU ever made: MC680xx

DAB — Mon, 18 Dec 2023 20:25:15 GMT

I agree, the design of the chip was very cool at the time.

RE: One of the Best CPU ever made: MC680xx

dougw — Mon, 18 Dec 2023 20:18:34 GMT

I think most would agree it was the best CPU architecture at the time. I am still a fan and I still have my Amiga. Unfortunately IBM didn't end up using it in the PC, the world would be different if they had.

RE: One of the Best CPU ever made: MC680xx

shabaz — Mon, 18 Dec 2023 17:23:27 GMT

It was an awesome chip : ) We studied it too, as part of a computer architecture curriculum.

After uni, I tried making a handheld 68k computer, using the neat "Dragonball VZ" chip (which was a 68k core). I got to the stage of creating a board test program, with a memory monitor to test the RAM/ROM and started writing a first application (which was merely writing its output to a memory buffer pretending to be a screen). This board was used just to test the power supplies, so it's not populated. The 68k chip was at bottom-right of the board, and the other main chips are Flash and SRAM.

Everything was an uphill struggle to do solo, there were no ESP32 etc for WiFi, so an external WiFi card was supposed to plug onto the PCMCIA connector in the photo below. The LCD screen was surplus from mobile phones and was only going to be 320x240 or something, but driving that was a pain too (there was no controller, so a CPLD was going to be used with a separate SRAM chip, to offload video refresh from the 68k).

I really liked the Freescale/Motorola chips because they had excellent bootloaders, so you could get the initial code for the 68K running over UART, and then push into Flash from there. No fancy JTAG/programmers needed!

RE: One of the Best CPU ever made: MC680xx

Jan Cumps — Mon, 18 Dec 2023 14:45:37 GMT

In my IT studies, learning assembler for the 68 was on the curriculum. And an exam exercise.

RE: One of the Best CPU ever made: MC680xx

scottiebabe — Mon, 18 Dec 2023 14:31:42 GMT

The Coldfire! [emoticon:34a31d54900f4d07b1322e895f940968] [emoticon:d3f592d49e434d7fb67e973881d4c367]

No need to load/store on registers, you get indirect addressing.

RE: Calling All EE Students - Build a Simple Flyback Converter to Win an Oscilloscope, DC Power Supply, Hot Air Soldering Station, and More!

shabaz — Sun, 15 Oct 2023 21:51:45 GMT

The prizes are a brilliant combination of test tools. The portable oscilloscope, plus the Electronic load, and the 1kW hot-air tool look great!! They would provide usefulness for many years during engineering careers. The RISC-V board looks interesting too.

This design challenge looks super-useful for those wanting to experiment or apply some theory and see what happens in practice.

If any students or other entrants need some advice during the challenge, for example if they get stuck, I'd be (and I'm sure others would be) happy to help remotely using the forum. Problems can be easily resolved by the collective knowledge of people on the forum.

I hope there are some high-voltage experiments! The photo belows shows how straightforward a flyback converter can be (with just a 555 and BJT and no feedback in this example). The photo is self-explanatory but I can sketch a circuit if anyone needs it. It is lighting up a small neon bulb. It also provides a slight electric shock if touched, due to the high voltage!

RE: Experimenting with Op Amps: Schmitt-trigger

phoenixcomm — Sat, 20 May 2023 20:09:33 GMT

[mention:acaf6a9338de4eef8f6717d5561ed01d:e9ed411860ed4f2ba0265705b8793d05] Jan, why in the world do you want to go down this rabbit hole? I still don't understand why. If you need a Schmitt Trigger then use a Schmitt Trigger. LOL I do like your bench.