Subversion Repositories openfpu64

OpenFPU64

============================

Peter Hüwe

V.0.1, Januar 2009, License: CC-by-sa

:author initials: PH

:email: peterhuewe@gmx.de

:license: CC-by-sa

About OpenFPU64

---------------

OpenFPU64 is a free and open source implementation of a double precision floating point unit.

The openFPU64 currently features:

* double precision

* Addition/Subtraction

* Multiplication

* rounding (to nearest even)

* subnormals/denormals

* validated against IEEE754 using TestFloat (http://www.jhauser.us/arithmetic/TestFloat.html)

* Compatible with Avalon Bus

* Wishbone interface will be provided soon

The openFPU64 is tested with a Cyclone II and a CycloneIII fpga.

Overview

--------

The openFPU64 consists of several parts:

* openfpu64.vhd         - contains the bus logic for the avalon bus, instantiate your own algorithms here

* fpu_package.vhd       - global constants and defines

* fpu_add.vhd           - Add/Sub algorithms

* fpu_mul.vhd           - Multiplication Algorithm with several embedded Multipliers

* fpu_mul_single.vhd - Multiplication Algorithm with only one embedded Multiplier (currently in development, has some bugs)

To use it in the NiosII environment you have to use the driver/library in

* nios-driver

The testbench needs also

* openfpu64_tb.vhd      - Testframework, consists of openfpu64_tb.head.vhd, openfpu64_tb.tail.vhd and the actual testcases which reside in tests/ (untar tests.tar.bz2)

* eis_helpers.vhd       - some nice conversion functions for std_logic_vectors, provided by Prof. Dr. Gundolf Kiefer.

Usage in QuartusII SOPC (tm)

----------------------------

In order to use openFPU64 copy all VHDL files  (*.vhd) and the TCL file (openfpu64_hw.tcl) to the root directory of your QuartusII Project.

(alternative: 'make quartus_distribution' and copy everything in openfpu64_quartus/ to the root directory of your Quartus II project)

Then open the QuartusII and from Quartus launch the SOPC Builder.

In SOPC Builder click new component in the left pane and select

File -> open and open the openfpu64_hw.tcl file.

By clicking on finish, the openFPU64 is added to your library.

Now add openFPU64 to your SOPC-design by double clicking on it, click Generate as usual.

In some rare cases your have to assign new Base and End Adresses,

clicking "System->Auto-Assign Base Adresses" does resolve this.

Now click Generate as usual, close SOPC Builder afterwards and compile your design as usual using Quartus.

Driver/Libary in NiosII:

------------------------

add the openfpu64.c and openfpu64.h files (in nios-driver)to your NiosII Project.

To use this library/driver, add the fpu.[ch] files to your application

and add these linker flags.

Click right on your application, choose properties, C/C++ Build

-> Linker -> General and type

"-Wl,--wrap,__adddf3,--wrap,__subdf3,--wrap,__muldf3"

For each implemented function, add another --wrap,__functioname

Development:

------------

If you'd like to do some development on openFPU64, you can use the Makefile together with GHDL (http://ghdl.free.fr/)

You can create several different testbenches by issuing one of these commands:

* empty_testsuite

* addsub_testsuite

* custom_testsuite

* add_testsuite

* sub_testsuite

* mul_testsuite

The custom_testsuite contains several hand crafted testsuites for ADD/SUB/MUL, the others are quite big (45k,95k testcases) and generated using TestFloat.

The testbench is made up of openfpu64_tb.head.vhd, openfpu64_tb.tail.vhd and the testscases in tests/.

If you want to change the testbench structure please DO NOT change openfpu64_tb.vhd but rather openfpu64_tb.head.vhd, otherwise your changes will be overwritten by make *_testsuite.

The empty testsuite is for 'resetting' the openfpu64_tb to be committed to svn.

Please use make empty_testsuite before checking your sources in.

Note:

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QuartusII, Nios, Cyclone, QuartusII SOPC Builders are registered Trademarks of Altera Corporation, 101 Innovation Drive, San Jose, California 95134, USA. All rights reserved.

Todo:

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Of course there is still a lot to do, e.g. adding more documentation.

Meanwhile, for questions contact me at peterhuewe@gmx.de and I'm glad to help you out