MIPS32R1 - 1 Jan 2014
---------------------

This is an implementation of the MIPS32 Release 1 processor.

This design was created by Grant Ayers and funded by the 
eXtensible Utah Multicore (XUM) project at the University of Utah
from 2010-2012. It was previously hosted on OpenCores as 'mips32r1'.
Feel free to send questions or feedback to ayers AT cs.stanford.edu.


Processor Details
-----------------

- Single-issue in-order 5-stage pipeline with full forwarding and hazard detection.
- Harvard architecture with separate instruction and data ports which can be 
  combined if desired.
- All required MIPS32 instructions are implemented, including hardware multiplication
  and division, fused multiply/adds, atomic load linked / store conditional, and
  unaligned loads and stores.
- Complete Coprocessor 0 allows ISA-compliant interrupts, exceptions, and user/kernel modes.
- No MMU. This is a bare-metal processor.
- No FPU, with toolchain support for software-based floating point.
- Hardware divider is small, multicycle, and runs asynchronously from the pipeline
  allowing some masking of latency.
- Memory interface is separate from the processor for flexibility with connecting
  various RAMs. It utilizes a four-way handshake.
- Hardware is Big-Endian by default and supports reverse-endian mode in User mode.
- Parameterized addresses for exception/interrupt vectors and boundary address
  between user/kernel regions.
- Extensive documentation in-source and elsewhere.
- Vendor-independent code.
- A clean, modular design written from scratch.

The project includes a standalone MIPS32 processor as well as a full System-on-Chip
design targeted for the Xilinx XUPV5-LX110T board. With minor changes (clock module,
BRAM module, and pin constraints) the SoC can run on many hardware platforms.


Other Hardware
--------------

The following MMIO hardware drivers are included as part of the SoC design:

- Basic single-master I2C driver.
- 16x2 LCD driver for Sitronix ST7066U, Samsung S6A0069X / KS0066U, Hitachi HD44780,
  SMOS SED1278, or other compatible hardware.
- LED driver.
- Piezo transducer driver.
- Switch input filter.
- 115200 baud 8-N-1 serial port using only Tx and Rx with configurable baud rate.
- 592 KB BRAM and clock generation for XUPV5 board.


Software Details
----------------

- The software toolchain is based on Binutils, GCC, and Newlib. It can be built for almost
  any platform, including unix-like environments and Windows (Cygwin). Instructions and
  toolchain source code is included in the project. The current toolchain uses
  Binutils 2.21, GCC 4.7.1 (mpfr 3.0.1, mpc 0.9, gmp 5.0.5), and Newlib 1.20.0.
  The toolchain supports Big- and Little-Endian code as well as software floating point.
  Newlib C library stubs (printf, etc.) are left unchanged.
- Several demos are written in C and assembly.
- The XUM bootloader is included, which loads programs from a PC to the FPGA. This is
  written in C# for Windows, however the boot protocol is simple and can be implemented
  in any operating system or not used at all.


Directory Layout
----------------

   Hardware:
      -> MIPS32_Standalone: Processor HDL only. Top file is "Processor.v".
      
      -> XUPV5-LX110T_SoC:  Full System-on-Chip for XUPV5 board and Xilinx ISE 14.1
                            Project Navigator. Useful as a starting point for other
                            boards as well. See "HOWTO" in this directory for more
                            information.
   
   Software:
      -> demos:             Software demos for XUM
      -> toolchain:         Instructions for creating a MIPS crosscompiler toolchain
      -> xum_bootloader:    A C# implementation of the XUM bootloader.


Legal
-----

All software and hardware included in this distribution is licensed under
the GNU LGPL. See the file 'LEGAL' in this same directory for more information.


Enjoy!