Hi Everyone!

I want to design a simplest of the microprocessors, that can work with
4-bits of operands and have fixed 3-bit instruction word. I have studied
AMD2901 for this purpose but that looks like a lot more than what i need.

Any idea will be greatly appreciated.

regards
naeemdotcom

naeemdotcom at hotmail.com wrote:
May you can try the old Intel 4004. That thing hasn't been around in
awhile, but simple
is definitely its strength.

LT

You could have a look at the picoblaze provided by Xilinx. It's a nice simple soft micro http://direct.xilinx.com/bvdocs/appnotes/xapp213.pdf ----- Original Message ----- From: Loi Tranleotran at a...> To: Date: Sat Apr 17 08:10:01 CEST 2004 Subject: [oc] simplest 4 bit microprocessor

The 4004 is worth looking at but you might also consider deriving something on your own from the PDP-8 line. It has a 12-bit instruction word with 3-bits for instruction one bit for indirect addressing one bit for page selection and 7-bits for address within page. This sounds complicated but is quite simple to impliment. It would help if a complete list of requirements is specified. In particular Is the design register only, memory only (predominantly), or register+memory. How much of each? Is there any I/O to be performed? If so, to what? Is multi-precision required (e.g. produce more than 4 bit results)? Is this to be Harvard or Von Neumann or other? Any other requirements that are important. Is this a class project? Jim ----- Original Message ----- From: Loi Tran To: Discussion list about free open source IP cores Sent: Saturday, April 17, 2004 1:10 AM Subject: Re: [oc] simplest 4 bit microprocessor naeemdotcom at hotmail.com wrote: >Hi Everyone! > >I want to design a simplest of the microprocessors, that can work with >4-bits of operands and have fixed 3-bit instruction word. I have studied >AMD2901 for this purpose but that looks like a lot more than what i need. > >Any idea will be greatly appreciated. > >regards >naeemdotcom >_______________________________________________ >http://www.opencores.org/mailman/listinfo/cores > > > May you can try the old Intel 4004. That thing hasn't been around in awhile, but simple is definitely its strength. LT _______________________________________________ http://www.opencores.org/mailman/listinfo/cores -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.opencores.org/forums.cgi/cores/attachments/20040503/67a4f0cc/attachment.htm

There is a very simple 8 bit CPU that fits in a 32 macrocell CPLD on the fpgacpu.org web site by Tim Boscke http://www.fpgacpu.org/links.html http://www.tu-harburg.de/%7Esetb0209/cpu/ It has an accumulator, 4 instructions and addressed 64 bytes of memory. It has a 2 bit instruction field and 6 bit address field. The 4 basic instructions are ADD, NOR, STO and JCC. It has a single accumulator and one addressing mode (absolute) I notice on Tim's web page he has a 4 bit CPU designed out of TTL parts that might be another way to go. I used Tims CPLD micro as a basis for learning how to design CPU cores. There is also the Micro8 on my web site, that might be good for your purpose although, again it's 8 bit, not 4 bit. It addressed 2K of memory and has an 8 bit index register as well as an accumulator. It uses a derivative of Tim's 4 basic instructions, and it has 4 addressing modes. http://members.optushome.com.au/jekent/FPGA.htm Hope that helps ... John. billy_rafferty at hotmail.com wrote: -- http://members.optushome.com.au/jekent -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.opencores.org/forums.cgi/cores/attachments/20040504/8a997661/attachment.htm