openlane VS picorv32

I would suggest Verilog-to-routing as the best open source tool ive used that deals with abstract circuit representations on an FPGA or similar architecture. but tools like Align and Magical both accept circuit inputs as netlists and have to represent them internally for generating layout so might be easier to understand their approach depending on your familiarity with analog circuits. One more option is to look up OpenLane flow, its more an amalgamation of lots of tools but definitely also represents circuits as a graph for manipulation later on.

There are open source alternatives. https://github.com/The-OpenROAD-Project/OpenLane

OpenLane

And, there is a project called 'The OpenROAD Project' which has created an open-source framework for digital back-end design/physical design. https://github.com/The-OpenROAD-Project/OpenLane

For "how the architecture is brought to silicon": Look at OpenLane. It's a complete Verilog to GDS flow, all open source and already used for some tape-outs. https://github.com/The-OpenROAD-Project/OpenLane

Maybe you can do something that can also go to an ASIC. Take a look at openlane flow, you don't need to do the backend since it is mostly script based and you can even send it to next Skywater submission. The major problem is that you currently don't have sram access so you need to create rams from logic if you need to.

I am not sure if you can do padding with this but dropping this down in case you haven't heard it: https://github.com/The-OpenROAD-Project/OpenLane

Specifically openlane (https://github.com/The-OpenROAD-Project/OpenLane is a great way to start, although it's very painful trying to do complex designs. However, they're pretty helpful answering questions on Gitter

https://github.com/efabless/openlane The README is very helpful

In contrast to most people here saying you NEED to spend money. I disagree with that. You can implement and simulate a SPI master/slave fully on your computer, no FPGA or other hardware required. There are simulation models for SPI peripherals you could use. For example: https://github.com/YosysHQ/picorv32/blob/master/picosoc/spiflash.v

The Pico RV32 is pretty small, and can go as low as about 750 LUTs, with most features elided. I don't know how Xilinix LUTs translate to Lattice though.

Picorv32: https://github.com/YosysHQ/picorv32

There are loads of free RISC-V cores that you can read the source of and run on cheap FPGAs. Take a look at PicoRV32: https://github.com/YosysHQ/picorv32

picorv32 is written in Verilog.

In short: it works, though the implementation lacks the crystal clarity of FemtoRV32 and PicoRV32. The core is larger than SERV but has higher IPC and (very arguably) a more conventional implementation. The compressed instruction set is easier to expand into regular RV32I instructions than it is to execute directly.

That is, reducing the number of LUT required to implement a CPU of a given ISA.

A basic RV32 CPU is down to 500-700 LUT.

    https://github.com/YosysHQ/picorv32

I've bought a cheap FPGA board (Sipeed Tang Nano 9K) because I want to implement a little 8 or 16-bit CPU. The FPGA has plenty of BRAM for such a little CPU, so I wouldn't even need to implement an SPI controller initially, but I want to implement a von Neumann architecture, and was wondering if the only way of doing so using single port (or semi dual port) RAM would be to use 2 cycles or more for memory transfer operations (one for loading the instruction, one for executing the actual memory transfer), or if there was any technique that could be used to avoid this without having to implement instruction-level parallelism. Even if not, references to understandable code implementing a simple memory interface would be appreciated. I looked at PicoRV32 but couldn't really understand its inner workings.

Have you looked at PicoRV32? https://github.com/YosysHQ/picorv32

What I mean is that you use the FPGA fabric to implement a soft-core CPU, like MicroBlaze (Xilinx) or Nios II (Altera/Intel) or RISC-V or any other CPU you like. Then you can do the MP3 or WAV signal decoding in software, which will be orders of magnitude easier to do than to do it in hardware. For a media player, this is more than adequate.