Subversion Repositories potato

# The Potato Processor

Potato is a simple processor for use in FPGAs, implementing the RV32I subset of the RISC-V ISA specification.

## Features

* Supports the full RV32I (RISC-V 32-bit integer subset) ISA.
* Additionally supports the csrr\* and sret instructions from the (previous) supervisor extension (draft).
* Includes an interface for the HTIF (Host/Target interface) registers, TOHOST and FROMHOST.
* Wishbone interface.

## Wishbone details

The wishbone interface for the processor is provided by the pp_wb_adapter module. Its details are as follows:

|-----------------------|---------------|
| Name                  | Value         |
| --------------------- | ------------- |
| Wishbone revision     | B4            |
| Interface type        | Master        |
| Address port width    | 32 bits       |
| Data port width       | 32 bits       |
| Data port granularity | 8 bits        |
| Maximum operand size  | 32 bits       |
| Endianess             | Little endian |
| Sequence of data xfer | Undefined     |
|---------------------------------------|

For all Wishbone interfaces included in this project, the Wishbone signals are prefixed with `wb` and suffixed by the
signal direction.

## Potato Processor Quick Start

To instantiate the processor, add the source files from the `src/` folder to your project. Use the `pp_potato` core to
instantiate a processor core with a Wishbone interface. Additional peripherals for use in Wishbone-based Potato systems
can be found in the `soc/` folder.

Use the `pp_core` module to instantiate a processor core with a more generic interface, for instance for use with block
memories. In this instance, connect the data and instruction memory ports directly to the block RAM modules/interfaces
and set the acknowledge inputs to `'1'`.

Interrupts are triggered when an IRQ signal is high and the corresponding mask bit is set in the control/status register.