This user joined on 03/31/2014.
zaphod
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monsonite
wrote 07/02/2014 at 06:58
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Hi Zaphod - any chance of putting the transistor level circuits of your various gates on this site. It would be good to see some reference designs and then characterise them for switching speed, fan out etc. I've started on the Nand2Tetris project and am currently doing a Logisim and EagleCAD version of the design as a bitslice made from 74xx00 Nand gates. Be great to dig one level deeper. Great project - keep up the good work.
zaphod
wrote 07/02/2014 at 20:23
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I thought I had already included the link, but here it is: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html (website seems to be down as of 2014-07-02 8:08 GMT). the specific circuits however are quite old. I'm pretty sure that the logic family I'm using is similar to the one used in the Saturn V's command computer, and the circuits appear in the engineers notebook series (circa ~1986 on page 36 and 37 in 'basic semiconductor circuits'). As for switching speed I know it is very low, however some of this is probably due to the computer being hand assembled on perfboard. fan out is also very low (~5 gates at best). if hyperphysics doesn't go back up here are the circuits as drawn by Forrest M. Mims: http://www.scribd.com/doc/129571828/Engineer-s-Mini-Notebook-Basic-Semiconductor-Circuits-by-Forrest-M-Mims-III
schuhumi
wrote 05/28/2014 at 19:34
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Thank you for the skull on my Logisim-Microcontroller project! Getting such attention from someone really knowing his business (your discrete computer is just astonishing) is a great motivation ;-) btw: I just built a stack into my µC and improved the assembler for easy function handling
zaphod
wrote 05/28/2014 at 20:07
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Hi, it's nice to know some one thinks I'm knowledgeable about this kind of thing, but I'm really not, you seem to know way more than me.
Hey Zaphod, thanks for the skull on the DDC-01 project. I hope your four bit computer project is going well. I always enjoy reading your project logs. They help me to stay motivated to work on my own stuff.