Commit c662be05 authored by bp's avatar bp

initial checkin

git-svn-id: https://www.forth-ev.de/repos/b16@2 3b8d8251-53f3-0310-8f3b-fd1cb8370982
parent 3abf29c5
GNU GENERAL PUBLIC LICENSE
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users. This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it. (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.) You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
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To protect your rights, we need to make restrictions that forbid
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you have. You must make sure that they, too, receive or can get the
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We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
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The precise terms and conditions for copying, distribution and
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GNU GENERAL PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License. The "Program", below,
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either verbatim or with modifications and/or translated into another
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the term "modification".) Each licensee is addressed as "you".
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Whether that is true depends on what the Program does.
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and give any other recipients of the Program a copy of this License
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you may at your option offer warranty protection in exchange for a fee.
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notice that there is no warranty (or else, saying that you provide
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the Program is not required to print an announcement.)
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Program,
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NO WARRANTY
11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
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OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
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END OF TERMS AND CONDITIONS
Appendix: How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) 19yy <name of author>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may
be called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program
`Gnomovision' (which makes passes at compilers) written by James Hacker.
<signature of Ty Coon>, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library. If this is what you want to do, use the GNU Library General
Public License instead of this License.
#
SOURCES = b16.lyx b16-eng.lyx Makefile \
b16.nw b16-eng.nw b16.v b16-eval.v b16-eval-test.v \
boot.asm b16.asm usb.asm b16_eval.rbf la.c b16.fs \
COPYING b16.pdf b16-eng.pdf hex2boot \
add-mem b16-usb-test.v usb-test.v usb.v \
b16-eval-usb.v b16-eval-usb-test.v usbphys.v ram1024.v stackram.v \
sieve.asm b16-gcc-slides.lyx gcc/b16.h gcc/b16.md.in
all: b16.v b16.pdf b16-eng.pdf la
gcc/b16.md: gcc/b16.md.in
m4 <$< >$@
%.nw: %.lyx
lyx --execute "buffer-export literate" $<
%.tex: %.nw
noweave -delay -latex $< | sed -e 's/1<<dep/1<{}<dep/g' >$@
latex $@
%.v: %.nw
notangle -Rb16.v $< >$@
%.dvi: %.tex
latex $<
%.ps: %.dvi
dvips -Pams -Pcmz -Ppdf $< -o $@
%.ps.gz: %.ps
gzip <$< >$@
%.pdf: %.ps
ps2pdf $< $@
la: la.c
gcc -O2 la.c -o la
dist: $(SOURCES)
mkdir b16
tar cf - $(SOURCES) | (cd b16; tar xf -)
tar jcf b16.tar.bz2 b16
rm -rf b16
#!/bin/bash
raml="$(grep 'RAM instance.*bootraml' exemplar.log | tail -1 | cut -f2 -d "'")_ix38"
ramh="$(grep 'RAM instance.*bootramh' exemplar.log | tail -1 | cut -f2 -d "'")_ix38"
awk "/\(instance $ramh/"' { print; print " (property LPM_FILE (string \"bootramh.mif\"))" }
'"/\(instance $raml/"' { print; print " (property LPM_FILE (string \"bootraml.mif\"))" }
!/\(instance ('"$ramh|$raml"')/ { print }' <b16_eval.edf >b16.edf
#LyX 1.3 created this file. For more info see http://www.lyx.org/
\lyxformat 221
\textclass literate-article
\begin_preamble
\usepackage[dvips,colorlinks=true,linkcolor=blue]{hyperref}
\end_preamble
\language american
\inputencoding auto
\fontscheme ae
\graphics default
\paperfontsize default
\spacing single
\papersize Default
\paperpackage widemarginsa4
\use_geometry 1
\use_amsmath 0
\use_natbib 0
\use_numerical_citations 0
\paperorientation portrait
\leftmargin 0.5in
\rightmargin 0.5in
\secnumdepth 3
\tocdepth 3
\paragraph_separation indent
\defskip medskip
\quotes_language english
\quotes_times 2
\papercolumns 2
\papersides 1
\paperpagestyle fancy
\layout Title
b16 --- A Forth Processor in an FPGA
\layout Author
\noun on
Bernd Paysan
\layout Standard
\begin_inset ERT
status Collapsed
\layout Standard
\backslash
lhead{
\end_inset
b16 --- A Forth Processor in an FPGA
\begin_inset ERT
status Collapsed
\layout Standard
}
\backslash
chead{
\end_inset
\noun on
Bernd Paysan
\noun default
\begin_inset ERT
status Collapsed
\layout Standard
}
\end_inset
\layout Abstract
This article presents architecture and implementation of the b16 stack processor.
This processor is inspired by
\noun on
Chuck Moore'
\noun default
s newest Forth processors.
The minimalistic design fits into small FPGAs and ASICs and is ideally
suited for applications that need both control and calculations.
The synthesizible implementation uses Verilog.
\layout Section*
Introduction
\layout Standard
Minimalistic CPUs can be used in many designs.
A state machine often is too complicated and too difficult to develop,
when there are more than a few states.
A program with subroutines can perform a lot more complex tasks, and is
easier to develop at the same time.
Also, ROM- and RAM blocks occupy much less place on silicon than
\begin_inset Quotes eld
\end_inset
random logic
\begin_inset Quotes erd
\end_inset
.
That's also valid for FPGAs, where
\begin_inset Quotes eld
\end_inset
block RAM
\begin_inset Quotes erd
\end_inset
is --- in contrast to logic elements --- plenty.
\layout Standard
The architecture is inspired by the c18 from
\noun on
Chuck Moore
\noun default
\begin_inset LatexCommand \cite{c18}
\end_inset
.
The exact instruction mix is different.
I traded
\family typewriter
2*
\family default
and
\family typewriter
2/
\family default
against division step and Forth-typical logic operations; these two instruction
s can be implemented as short macro.
Also, this architecture is byte-addressed.
\layout Standard
The original concept (which was synthesizible, and could execute a small
sample program) was written in an afternoon.
The current version is somewhat faster, and really runs on a Altera Flex10K30E
on a FPGA evaluation board from
\noun on
Hans Eckes
\noun default
.
Size and speed of the processor can be evaluated.
\layout Description
Flex10K30E About 600 LCs, the unit for logic cells in Altera
\begin_inset Foot
collapsed true
\layout Standard
A logic cell can compute a logic function with four inputs and one output,
or a full-adder, and also contains a flip-flop.
\end_inset
.
The logic to interface with the eval board needs another 100 LCs.
The slowest model runs at up to 25MHz.
\layout Description
Xfab\SpecialChar ~
0.6µ
\begin_inset Formula $\sim$
\end_inset
1mm² with 8 stack elements, that's a technology with only 2 metal layers.
\layout Description
TSMC\SpecialChar ~
0.5µ
\begin_inset Formula $<$
\end_inset
0.4mm² with 8 stack elements, this technology has 3 metal layers.
With a somewhat optimized ALU the 5V library reaches 100MHz.
\layout Standard
The complete development (excluding board layout and test synthesis for
ASIC processes) was done with free or zero cost tools.
Icarus Verilog in the current version is quite useful for projects in this
order of magnitude, and Quartus II Web Edition is a big chunk to download,
but doesn't cost anything (downside: Windows NT, the version for real operating
system costs real money).
\layout Standard
A word about Verilog: Verilog is a C-like language, but tailored for the
purpose to simulate logic, and to write synthesizible code.
Variables are bits and bit vectors, and assignments are typically non-blocking,
i.e.
on assignments first all right sides are computed, and the left sides are
modified afterwards.
Also, Verilog has events, like changing of values or clock edges, and blocks
can wait on them.
\layout Section
Architectural Overview
\layout Standard
The core components are
\layout Itemize
An ALU
\layout Itemize
A data stack with top and next of stack (T and N) as inputs for the ALU
\layout Itemize
A return stack, where the top of return stack (R) can be used as address
\layout Itemize
An instruction pointer P
\layout Itemize
An address register A
\layout Itemize
An address latch
\family typewriter
addr
\family default
, to address external memory
\layout Itemize
An instruction latch I
\layout Standard
Figure
\begin_inset LatexCommand \ref{blockdiagram}
\end_inset
shows a block diagram.
\layout Standard
\begin_inset Float figure
wide false
collapsed false
\layout Standard
\align center
\begin_inset Graphics
filename b16.eps
display color
width 100col%
\end_inset
\layout Caption
Block Diagram
\begin_inset LatexCommand \label{blockdiagram}
\end_inset
\end_inset
\layout Subsection
Register
\layout Standard
In addition to the user-visible latches there are control latches for external
RAM (
\family typewriter
rd
\family default
and
\family typewriter
wr
\family default
), stack pointers (
\family typewriter
sp
\family default
and
\family typewriter
rp
\family default
), a carry
\family typewriter
c
\family default
and the flag
\family typewriter
incby
\family default
, by which
\family typewriter
addr
\family default
is incremented.
\layout Standard
\added_space_top medskip \added_space_bottom medskip \align center
\begin_inset Tabular
<lyxtabular version="3" rows="12" columns="2">
<features>
<column alignment="center" valignment="top" leftline="true" width="0pt">
<column alignment="left" valignment="top" leftline="true" rightline="true" width="0pt">
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
\emph on
Name
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
\emph on
Function
\end_inset
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
T
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
Top of Stack
\end_inset
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
N
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
Next of Stack
\end_inset
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
I
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\layout Standard
Instruction Bundle
\end_inset
</cell>
</row>
<row topline="true">