best FPA soft processor implementation for learning purposes

[shaiko]

Hello people,

I want to learn integrating soft processors on FPGAs.
Not interested in either Nios or Microblaze as they're platform dependent.

I'm looking for a free, platform independent alternative with good C compiler support.

This is solely for learning purposes - so the capabilities of the device don't matter

What soft CPU should I begin with?
P.S: I write in VHDL

 

[tariq786]

Is ARM a bad choice? If so why?

 

[Marcel Majoor]

I would go for Altium Designer.
You might think it is only a schematic/PCB design software, but you can also create complete soft processors in FPGA (you can choose from different kind of processors), includes a C compiler, libraries to control ethernet and such, etc.
They can also supply a complete development environment for soft processor FPGA development, named NanoBoard.
For a NanoBoard introduction go here: **broken link removed**

 

[shaiko]

Thanks Marcel.

Do you have to use the Altium designer software to integrate the soft CPU? or it can be done with text .vhd files only?


tariq,
I don't know of any ARM soft processor implementations that are free and plattform independent...

 

[RetroTechie]

Browse the processor section on OpenCores. 8, 16 or 32 bit CPU would depend on how simple/complex architecture you feel comfortable starting with. Pick a re-implementation of a well known CPU, and finding a decent C compiler for it shouldn't be too hard. Pick one that's already used in other project(s), and you have sample application if needed.

For example:

• Amber (ARM-compatible)
• AVR Core
• cpu6502_tc
• miniMIPS
• OpenRISC 1000
• Plasma
• RISC5x
• T65
• T80
• TG68

 

[shaiko]

Can you recommend one? Which of the above has the best C compiler support?
Which one is the most used?

 

[Marcel Majoor]

The whole soft processor in Altium Designer is 'transparent' to the user. Basically you are not aware that is implemented into a FPGA for that matter. You can even run-time debug the (C) application you have written for that soft processor. Setup of connections (internally/externally) and use of soem of the predefined 'libraries' is mostly done in a graphical manner.
If you only implement the soft processor in the FPGA, then the user will not even be aware of any vhdl/verilog code. Although it is possible I think to use your own vhdl code, it is not typical in this design process.

 

[shaiko]

Do I have to own a licence for Altium designer in order to implement it?

 

[Marcel Majoor]

Yes, Altium designer is not free, nor do they have a 'lite' (free) version (as far as I know). Not sure if they have special student licenses.
If I'm not mistaken, you get a 1 year 'free' subscription of Altium designer if you buy a NanoBoard. Not sure this will be a subscription for the full product or just the 'soft' design part (you have to check that out yourself by reading the information at Altium; a year ago or so it was not the full product).

 

[shaiko]

what about the msp430 ?

 

[Marcel Majoor]

Altium Designer does not support the MSP430 directly, but maybe the TSK165 is 'compatible' with it (it is based on a 16-bit RISC). The TSK3000 is a 32-bit RISC processor.
For soft designs, independent from the FPGA used, you are limited to the devices like TSK51, TSK52, TSK80, TSK165, TSK3000 (these are the 8051/8052/Z80/165x/3000 equivalents).
If you are using a specific FPGA then you can also build software for Actel COREMP7 (ARM), Altera NIOS2, Xilinx MICROBLAZE, Xilinx POWERPC (additional licenses of the FPGA manufacturer may be needed I think, unless the processor is already build in, like the PowerPC for Virtex FPGA's).