Hi, does anyone have a complete schematic for an 8 bit TTL microprocessor design? I'm working on it as a project. I've found one for 4 bit from http://www.tamalsaha.com/4-bit-microprocessor-design.html
but is there an improved version of this design to 8 bit?
Many thanks!

 

diagram shows 4-bit design but it is generic architecture, which can be expanded to 8 or any number of bits.
btw, there is nothing in that block diagram that makes it TTL or NMOS or CMOS or whatever...
same goes for this example
http://ocw.capilanou.ca/computing-s...se_files/programming/ProgrammableMachine.html

 

Thanks. How to expand it to 8 bits design?

 

The circuit reference you posted is for a 4/8 bit design. It can be used to build either.

 

step 1. print the diagram
step 2. get a red pen
step 3. cross every "4" on the diagram
step 4. write "8" next to every "4" that was crossed
step 5. think what would take to make that 16-bit design

 

The circuit reference you posted is for a 4/8 bit design. It can be used to build either.

How exactly can I build 8 bit microprocessor from the schematic? Double the ALU? I'm not sure as there are already two 74LS181 there.

 

How exactly can I build 8 bit microprocessor from the schematic? Double the ALU? I'm not sure as there are already two 74LS181 there.

Since a 74LS181 is a 4-bit ALU then two of them will handle 8 bits. You don't need to add any more.

 

step 1. print the diagram
step 2. get a red pen
step 3. cross every "4" on the diagram
step 4. write "8" next to every "4" that was crossed
step 5. think what would take to make that 16-bit design

My project is to build an 8 bit microprocessor, not a 16 bit.

 

Since a 74LS181 is a 4-bit ALU then two of them will handle 8 bits. You don't need to add any more.

Thanks. Can you help me in details to expand the design to 8bit? I need to get it done in three weeks...

 

Thanks. Can you help me in details to expand the design to 8bit? I need to get it done in three weeks...

The reference in your first post has a schematic diagram of the circuit. What more detail could you need?

 

Do I smell a Rodney Robot Design?
..
Dave
Phoenix, AZ

 

Nope. This is the fundamental requirements of my project:
Project Title: 8-bit Microprocessor Emulator
Proposed Tools: TTL logic chips, Microcontroller
Project Outcome
1. A discrete hardware emulator of a simple 8-bit CISC microprocessor using TTL logic chips.
2. Able to run a subset of assembly code compiled on a PC and downloaded to the emulator.
3. Able to display the data on the data-path of the processor.

 

This does have an 8 bit address, but only a 4 bit instruction length.

Is this what you want as 8 bit?

P.S. I don't want to seem rude, but as this is your project, shouldn't you be designing it yourself? I don't know how unis work - are you allowed to copy circuits?

 

Do you know how "message in space" works?

You can use this as starting point for a microprocessor.

For message in space, the PC always increments by one.
For microprocessor, you need to change this, add branching.

However it's a lot of effort actually even only to build message in space using TTL only. I have done this a while ago, but it was so much effort to wire, it was scrapped.

3 weeks for TTL microprocessor? Seriously?

I would use WINCUPL eventually to simulate the logic, and use message in space principle as a starting point.

If you are allowed to use small microcontrollers, things get easier but you need to be good at using these.

On a public forum you can get some hints to help you shortcut, to get a starting point, but it's far too much and far too complex.

And simply using a ready-made schematic is bad for this.

Really try to build message in space using WINCUPL etc., and see if you can add branching as well.

The ring counter address pointer (or register) for the message data is changed, to become PC (program counter)!

 

To give you an idea of time, I'm following the progress of someone who is making a computer out DTL. It has been over three months, and he says he's only 1/20th through the project.