icestorm/docs/index.html

<title>Project IceStorm</title>
<h1>Project IceStorm</h1>

<p>
<b>2015-05-27:</b> We have a working fully Open Source flow with <a href="http://www.clifford.at/yosys/">Yosys</a> and <a href="https://github.com/cseed/arachne-pnr">Arachne-pnr</a>! Video: <a href="http://youtu.be/yUiNlmvVOq8">http://youtu.be/yUiNlmvVOq8</a><br/>
<b>2015-04-13:</b> Complete rewrite of IceUnpack, added IcePack, some major documentation updates<br/>
<b>2015-03-22:</b> First public release and short YouTube video demonstrating our work: <a href="http://youtu.be/u1ZHcSNDQMM">http://youtu.be/u1ZHcSNDQMM</a>
</p>

<h2>What is Project IceStorm?</h2>

<p>
Project IceStorm aims at documenting the bitstream format of Lattice iCE40
FPGAs and providing simple tools for analyzing and creating bitstream files.
At the moment the focus of the project is on the HX1K-TQ144 device, but
most of the information is device-independent.
</p>

<h2>Why the Lattice iCE40?</h2>

<p>
It has a very minimalistic architecture with a very regular structure. There are not many
different kinds of tiles or special function units. This makes it both ideal for
reverse engineering and as a reference platform for general purpose FPGA tool development.
</p>

<p>
Also, with the <a href="http://www.latticesemi.com/icestick">iCEstick</a> there is
a cheap and easy to use development platform available, which makes the part interesting
for all kinds of projects.
</p>

<h2>What is the Status of the Project?</h2>

<p>
We have enough bits mapped that we can create a functional verilog model for almost all 
bitstreams generated by Lattice iCEcube2 for the iCE40 HX1K-TQ144, as long as no
block memories or PLLs are used. (Both are fully documented, but the
<tt>icebox_vlog.py</tt> script does not create verilog models for them yet.)
</p>

<p>
Next on the TODO list: PLLs, Timing Analysis, support for HX8K chips.
</p>

<h2>What is the Status of the Fully Open Source iCE40 Flow?</h2>

<p>
Synthesis for iCE40 FPGAs can be done with <a href="http://www.clifford.at/yosys/">Yosys</a>.
Place-and-route can be done with <a href="https://github.com/cseed/arachne-pnr">arachne-pnr</a>.
Here is an example script for implementing and programming the <a
href="https://github.com/cseed/arachne-pnr/tree/master/examples/rot">rot example from
arachne-pnr</a> (this example targets the iCEstick development board):
</p>

<pre style="padding-left: 3em">yosys -p "synth_ice40 -blif rot.blif" rot.v
arachne-pnr -d 1k -p rot.pcf rot.blif -o rot.txt
icepack rot.txt rot.bin
iceprog rot.bin</pre>

<h2>Where are the Tools?</h2>

<p>
Here is the current snapshot of our toolchain: <a href="icestorm-snapshot-150526.zip">icestorm-snapshot-150526.zip</a><br/>
<i>This is work under construction and highly experimental! Use at your own risk!</i>
</p>

<p style="margin-bottom: 0.5em;">
All snapshots in reverse chronological order:
</p>

<ul style="margin-top: 0.5em;">
<li><a href="icestorm-snapshot-150526.zip">icestorm-snapshot-150526.zip</a></li>
<li><a href="icestorm-snapshot-150413.zip">icestorm-snapshot-150413.zip</a></li>
<li><a href="icestorm-snapshot-150401.zip">icestorm-snapshot-150401.zip</a></li>
<li><a href="icestorm-snapshot-150322.zip">icestorm-snapshot-150322.zip</a></li>
</ul>

<h3>IcePack/IceUnpack</h3>

<p>
The <tt>iceunpack</tt> program converts an iCE40 <tt>.bin</tt> file into the IceBox ASCII format
that has blocks of <tt>0</tt> and <tt>1</tt> for the config bits for each tile in the chip. The
<tt>icepack</tt> program converts such an ASCII file back to an iCE40 <tt>.bin</tt> file.
</p>

<h3>IceBox</h3>

<p>
A python library and various tools for working with IceBox ASCII files and accessing
the device database. For example <tt>icebox_vlog.py</tt> converts our ASCII file
dump of a bitstream into a verilog file that implements an equivalent circuit.
</p>

<h3>IceProg</h3>

<p>
A small driver programm for the FTDI-based programmer used on the iCEstick and HX8K development boards.
</p>

<p>
<i>The tools are written by Clifford Wolf. IcePack/IceUnpack is based on a reference implementation provided by Mathias Lasser.</i>
</p>

<h2>Where is the Documentation?</h2>

<p>
Recommended reading:
<a href="http://www.latticesemi.com/~/media/LatticeSemi/Documents/DataSheets/iCE/iCE40LPHXFamilyDataSheet.pdf">Lattice iCE40 LP/HX Family Datasheet</a>,
<a href="http://www.latticesemi.com/~/media/LatticeSemi/Documents/TechnicalBriefs/SBTICETechnologyLibrary201412.pdf">Lattice iCE Technology Library</a>
(Especially the three pages on "Architecture Overview", "PLB Blocks", "Routing", and "Clock/Control Distribution Network" in
the Lattice iCE40 LP/HX Family Datasheet. Read that first, then come back here.)
</p>

<p>
The FPGA fabric is divided into tiles. There are IO, RAM and LOGIC tiles.
</p>

<ul>
<li><a href="logic_tile.html">LOGIC Tile Documentation</a></li>
<li><a href="io_tile.html">IO Tile Documentation</a></li>
<li><a href="ram_tile.html">RAM Tile Documentation</a></li>
<li><a href="format.html">The Bitstream File Format</a></li>
<li><a href="bitdocs/">Tile Bits Reference Docs</a></li>
</ul>

<p>
The <tt>iceunpack</tt> program can be used to convert the bitstream into an ASCII file
that has a block of <tt>0</tt> and <tt>1</tt> characters for each tile. For example:
</p>

<pre style="padding-left: 3em">.logic_tile 12 12
000000000000000000000000000000000000000000000000000000
000000000000000000000011010000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000001011000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000
000000000000000000000000001000001000010101010000000000
000000000000000000000000000101010000101010100000000000</pre>

<p>
This bits are referred to as <tt>B<i>y</i>[<i>x</i>]</tt> in the documentation. For example, <tt>B0</tt> is the first
line, <tt>B0[0]</tt> the first bit in the first line, and <tt>B15[53]</tt> the last bit in the last line.
</p>

<p>
The <tt>icebox_explain.py</tt> program can be used to turn this block of config bits into a description of the cell
configuration:
</p>

<pre style="padding-left: 3em">.logic_tile 12 12
LC_7 0101010110101010 0000
buffer local_g0_2 lutff_7/in_3
buffer local_g1_4 lutff_7/in_0
buffer sp12_h_r_18 local_g0_2
buffer sp12_h_r_20 local_g1_4</pre>

<p>
IceBox contains a database of the wires and configuration bits that can be found in iCE40 tiles. This database can be accessed
via the IceBox Python API. But IceBox is a large hack. So it is recommended to only use the IceBox API
to export this database into a format that fits the target application. See <tt>icebox_chipdb.py</tt> for
an example program that does that.
</p>

<p>
The recommended approach for learning how to use this documentation is to synthesize very simple circuits using
Lattice iCEcube2, run our toolchain on the resulting bitstream files, and analyze the results using the HTML export of the database
mentioned above. <tt>icebox_vlog.py</tt> can be used to convert the bitstream to verilog. The output file of
this tool will also outline the signal paths in comments added to the generated verilog.
</p>

<p>
For example, using the <tt>top_bitmap.bin</tt> from the following Verilog and PCF files:
</p>

<pre style="padding-left: 3em">module top (input a, b, output y);
  assign y = a &amp; b;
endmodule

set_io a 1
set_io b 10
set_io y 11</pre>

<p>
We would get something like the following <tt>icebox_explain.py</tt> output:
</p>

<pre style="padding-left: 3em">$ iceunpack top_bitmap.bin top_bitmap.txt
$ icebox_explain top_bitmap.txt
Reading file 'top_bitmap.txt'..
Fabric size (without IO tiles): 12 x 16

.io_tile 0 10
IOB_1 PINTYPE_0
IOB_1 PINTYPE_3
IOB_1 PINTYPE_4
IoCtrl IE_0
IoCtrl IE_1
IoCtrl REN_0
buffer local_g1_2 io_1/D_OUT_0
buffer logic_op_tnr_2 local_g1_2

.io_tile 0 14
IOB_1 PINTYPE_0
IoCtrl IE_1
IoCtrl REN_0
buffer io_1/D_IN_0 span4_horz_28

.io_tile 0 11
IOB_0 PINTYPE_0
IoCtrl IE_0
IoCtrl REN_1

.logic_tile 1 11
LC_2 0000000001010101 0000
buffer local_g1_4 lutff_2/in_3
buffer local_g3_1 lutff_2/in_0
buffer neigh_op_lft_4 local_g1_4
buffer sp4_r_v_b_41 local_g3_1

.logic_tile 2 14
routing sp4_h_l_41 sp4_v_b_4</pre>

<p>
And something like the following <tt>icebox_vlog.py</tt> output:
</p>

<pre style="padding-left: 3em">$ icebox_vlog top_bitmap.txt
// Reading file 'top_bitmap.txt'..

module chip (output io_0_10_1, input io_0_11_0, input io_0_14_1);

wire io_0_10_1;
// io_0_10_1
// (0, 10, 'io_1/D_OUT_0')
// (0, 10, 'io_1/PAD')
// (0, 10, 'local_g1_2')
// (0, 10, 'logic_op_tnr_2')
// (0, 11, 'logic_op_rgt_2')
// (0, 12, 'logic_op_bnr_2')
// (1, 10, 'neigh_op_top_2')
// (1, 11, 'lutff_2/out')
// (1, 12, 'neigh_op_bot_2')
// (2, 10, 'neigh_op_tnl_2')
// (2, 11, 'neigh_op_lft_2')
// (2, 12, 'neigh_op_bnl_2')

wire io_0_11_0;
// io_0_11_0
// (0, 11, 'io_0/D_IN_0')
// (0, 11, 'io_0/PAD')
// (1, 10, 'neigh_op_tnl_0')
// (1, 10, 'neigh_op_tnl_4')
// (1, 11, 'local_g1_4')
// (1, 11, 'lutff_2/in_3')
// (1, 11, 'neigh_op_lft_0')
// (1, 11, 'neigh_op_lft_4')
// (1, 12, 'neigh_op_bnl_0')
// (1, 12, 'neigh_op_bnl_4')

wire io_0_14_1;
// io_0_14_1
// (0, 14, 'io_1/D_IN_0')
// (0, 14, 'io_1/PAD')
// (0, 14, 'span4_horz_28')
// (1, 11, 'local_g3_1')
// (1, 11, 'lutff_2/in_0')
// (1, 11, 'sp4_r_v_b_41')
// (1, 12, 'sp4_r_v_b_28')
// (1, 13, 'neigh_op_tnl_2')
// (1, 13, 'neigh_op_tnl_6')
// (1, 13, 'sp4_r_v_b_17')
// (1, 14, 'neigh_op_lft_2')
// (1, 14, 'neigh_op_lft_6')
// (1, 14, 'sp4_h_r_41')
// (1, 14, 'sp4_r_v_b_4')
// (1, 15, 'neigh_op_bnl_2')
// (1, 15, 'neigh_op_bnl_6')
// (2, 10, 'sp4_v_t_41')
// (2, 11, 'sp4_v_b_41')
// (2, 12, 'sp4_v_b_28')
// (2, 13, 'sp4_v_b_17')
// (2, 14, 'sp4_h_l_41')
// (2, 14, 'sp4_v_b_4')

assign io_0_10_1 = /* LUT    1 11  2 */ io_0_11_0 ? io_0_14_1 : 0;

endmodule</pre>

<p>
<hr>
</p>

<p>
In papers and reports, please refer to Project IceStorm as follows: Clifford Wolf, Mathias Lasser. Project IceStorm. http://www.clifford.at/icestorm/,
e.g. using the following BibTeX code:
</p>

<pre>@MISC{IceStorm,
	author = {Clifford Wolf and Mathias Lasser},
	title = {Project IceStorm},
	howpublished = "\url{http://www.clifford.at/icestorm/}"
}</pre>

<p>
<hr>
</p>

<p>
<i>Documentation mostly by Clifford Wolf &lt;clifford@clifford.at&gt; in 2015. Based on research by Mathias Lasser and Clifford Wolf.<br/>
Buy an <a href="http://www.latticesemi.com/icestick">iCEstick</a> from Lattice and see what you can do with the information provided here. Buy a few because you might break some..</i>
</p>