Inspired by Jeff Laughton's simple computer, I've removed the program counter and replaced it with a latch. Programming is now more laborious, but program flow has been made more flexible.
http://laughtonelectronics.com/Arcana/One-bit%20computer/One-bit%20computer.html
http://laughtonelectronics.com/Arcana/One-bit%20computer/One-bit%20computer.html
Nice
what are the display's your using?
Wow!
I'm not sure I get the point of doing what you're doing. It seems like (to make a Rick and Morty joke) you've just designed a program counter with extra steps.
The 74LS161 chip is a four-bit binary counter, and you can chain two of them together to make an eight-bit counter. And it does have the ability to update its state with an arbitrary input, in order to execute jump instructions. And it's still just two chips; I know you expressed a desire to keep the chip count to a minimum.
What are the little red/blue light/LED modules on here? I tried searching but can't find anything like them (not entirely sure what to search for though :-))
Great video. I'm definitely gonna have to try this myself. Only difference I would make would be to use an AT28C16 EEPROM in place of one or both SRAM chips. I've found they still (mostly)enter a write cycle using a tactile switch without worrying much about the write pulse being 50 to 1000ns as the datasheet suggests. Ben Eater made a video about them and used an RC circuit for the timing but it seems you can get away without using it. Probably not the greatest idea, though.
Where do I get that led display?
I just started on this build and looking at the data sheet for the 555 it says pin 4 should be taken to vcc to avoid false triggering. Yet you have pin 4 floating. Any particular reason why?
can you list all of the component, please…. thanks.
Doesn't this make is a Harvard architecture machine rather than a vonn Neuman architecture as it requires seperate memory more Instructions and Data?
Mr. Ilett, I really like your videos and especially this project, but this is the most stupid solution for program counter I've ever seen 😀 What you actually need is parallel output counter but with load / set function, so you can set any starting number and let it count. This is important for branching. There is no point of needing RAM for PC. You need something like TI SN74AS867.
Very interesting series. Thank you for taking the time to make these videos.
On a side note, you may want to take a look at the 269 in the 7400 series ICs. The 269 is a 8 bit biinary up/down counter with the ability to be preset with an initial starting value. This should eliminate the need to have a second RAM chip dedicated for use as a program counter. Looking on ebay these should be readily available in 74F flavor and should help keep the overall cost low.