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<title>Project IceStorm – UltraPlus Features Documentation</title>
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<h1>Project IceStorm – UltraPlus Features Documentation</h1>
<p>
<i><a href=".">Project IceStorm</a> aims at documenting the bitstream format of Lattice iCE40
FPGAs and providing simple tools for analyzing and creating bitstream files.
This is work in progress.</i>
</p>
<p>The ice40 UltraPlus devices have a number of new features compared to the older LP/HX series
devices, in particular:
<ul>
<li>Internal DSP units, capable of 16-bit multiply and 32-bit accumulate.</li>
<li>1Mbit of extra single-ported RAM, in addition to the usual BRAM</li>
<li>Internal hard IP cores for I2C and SPI</li>
<li>2 internal oscillators, 48MHz (with divider) and 10kHz</li>
<li>24mA constant current LED ouputs and PWM hard IP</li>
</ul>
In order to implement these new features, a significant architecural change has been made: the
left and right sides of the device are no longer IO, but instead DSP and IPConnect tiles.
</p>
<h2>DSP Tiles</h2>
<p>Each MAC16 DSP comprises of 4 DSP tiles, all of which perform part of the DSP function and have
different routing bit configurations. Structually they are similar to logic tiles, but with the DSP
function wired into where the LUTs and DFFs would be. The four types of DSP tiles will be referred to
as DSP0 through DSP3, with DSP0 at the lowest y-position. One signal CO, is also routed through the
IPConnect tile above the DSP tile, referred to as IPCON4 in this context.
A work-in-progress effort to determine where signals and configuration bits are located is below:</p>
<p>
<strong>Signal Assignments</strong><br/>
<table class="ctab">
<tr><th>SB_MAC16 port</th><th>DSP0</th><th>DSP1</th><th>DSP2</th><th>DSP3</th><th>IPCON4</th></tr>
<tr><td>CLK</td><td>-</td><td>-</td><td>lutff_global/clk</td><td>-</td><td>-</td></tr>
<tr><td>CE</td><td>-</td><td>-</td><td>lutff_global/cen</td><td>-</td><td>-</td></tr>
<tr><td>C[7:0]</td><td>-</td><td>-</td><td>-</td><td>lutff_[7:0]/in_3</td><td>-</td></tr>
<tr><td>C[15:8]</td><td>-</td><td>-</td><td>-</td><td>lutff_[7:0]/in_1</td><td>-</td></tr>
<tr><td>A[7:0]</td><td>-</td><td>-</td><td>lutff_[7:0]/in_3</td><td>-</td><td>-</td></tr>
<tr><td>A[15:8]</td><td>-</td><td>-</td><td>lutff_[7:0]/in_1</td><td>-</td><td>-</td></tr>
<tr><td>B[7:0]</td><td>-</td><td>lutff_[7:0]/in_3</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>B[15:8]</td><td>-</td><td>lutff_[7:0]/in_1</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>D[7:0]</td><td>lutff_[7:0]/in_3</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>D[15:8]</td><td>lutff_[7:0]/in_1</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>IRSTTOP</td><td>-</td><td>lutff_global/s_r</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>IRSTBOT</td><td>lutff_global/s_r</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>ORSTTOP</td><td>-</td><td>-</td><td>-</td><td>lutff_global/s_r</td><td>-</td></tr>
<tr><td>ORSTBOT</td><td>-</td><td>-</td><td>lutff_global/s_r</td><td>-</td><td>-</td></tr>
<tr><td>AHOLD</td><td>-</td><td>-</td><td>lutff_0/in_0</td><td>-</td><td>-</td></tr>
<tr><td>BHOLD</td><td>-</td><td>lutff_0/in_0</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>CHOLD</td><td>-</td><td>-</td><td>-</td><td>lutff_0/in_0</td><td>-</td></tr>
<tr><td>DHOLD</td><td>lutff_0/in_0</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>OHOLDTOP</td><td>-</td><td>-</td><td>-</td><td>lutff_1/in_0</td><td>-</td></tr>
<tr><td>OHOLDBOT</td><td>lutff_1/in_0</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>ADDSUBTOP</td><td>-</td><td>-</td><td>-</td><td>lutff_3/in_0</td><td>-</td></tr>
<tr><td>ADDSUBBOT</td><td>lutff_3/in_0</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>OLOADTOP</td><td>-</td><td>-</td><td>-</td><td>lutff_2/in_0</td><td>-</td></tr>
<tr><td>OLOADBOT</td><td>lutff_2/in_0</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>CI</td><td>lutff_4/in_0</td><td>-</td><td>-</td><td>-</td><td>-</td></tr>
<tr><td>O[31:0]</td><td>mult/O_[7:0]</td><td>mult/O_[15:8]</td><td>mult/O_[23:16]</td><td>mult/O_[31:24]</td><td>-</td></tr>
<tr><td>CO</td><td>-</td><td>-</td><td>-</td><td>-</td><td>slf_op_0</td></tr>
</table>
</p>
<p>
<strong>Configuration Bits</strong><br/>
<p>The DSP configuration bits mostly follow the order stated in the ICE Technology Library document, where they are described as<span style="font-family:monospace">CBIT[24:0]</span>. For most DSP tiles,
these follow a logical order where <span style="font-family:monospace">CBIT[7:0]</span> maps to DSP0 <span style="font-family:monospace">CBIT[7:0]</span>; <span style="font-family:monospace">CBIT[15:8]</span>
to DSP1 <span style="font-family:monospace">CBIT[7:0]</span>, <span style="font-family:monospace">CBIT[23:16]</span> to DSP2 <span style="font-family:monospace">CBIT[7:0]</span>
and <span style="font-family:monospace">CBIT[24]</span> to DSP3 <span style="font-family:monospace">CBIT0</span>.
</p>
<p>However, there are some locations where configuration bits are swapped between DSP tiles and IPConnect tiles. For example, DSP1 (0, 16) <span style="font-family:monospace">CBIT[4:3]</span> is used
for the internal oscillator, and the DSP configuration bits are then located in IPConnect tile (0, 19) <span style="font-family:monospace">CBIT[6:5]</span>.</p>
<p>The exact permutations are not yet known, but a script will be developed to find them.</p>
<p>
<strong>Other Implementation Notes</strong><br/>
<p>
All active DSP tiles, and all IPConnect tiles whether used or not, have some bits set which reflect their logic tile heritage. The <span style="font-family:monospace">LC_<em>x</em></span>
bits which would be used to configure the logic cell, are set to the below pattern for each "logic cell" (interpreting them like a logic tile):<br/>
<br><span style="font-family:monospace">0000111100001111 0000</span><br/><br/>
Coincidentally or not, this corresponds to a buffer passing through input 2 to the output. For each "cell" the cascade bit <span style="font-family:monospace">LC0<em>x</em>_inmux02_5</span> is
also set, effectively creating one large chain, as this connects input 2 to the output of the previous LUT. It is not yet known if this serves any purpose, or is merely a remainder of Lattice's
internal testing.
</p>
</p>
<h2>IPConnect Tiles</h2>
<p>IPConnect tiles are used for connections to all of the other UltraPlus features, such as I2C/SPI, SPRAM, RGB and oscillators. Like DSP tiles,
they are structually similar to logic tiles. The outputs of IP functions are connected to nets named <span style="font-family:monospace">slf_op_0</span> through <span style="font-family:monospace">slf_op_7</span>,
and the inputs use the LUT/FF inputs in the same way as DSP tiles.</p>
<h2>Internal Oscillators</h2>
Both of the internal oscillators are connected through IPConnect tiles, with their outputs optionally connected to the global networks,
by setting the "padin" extra bit (the used global networks 4 and 5 don't have physical pins on UltraPlus devices).
<h3>SB_HFOSC</h3>
<p>The <span style="font-family:monospace">CLKHFPU</span> input connects through IPConnect tile (0, 29) input <span style="font-family:monospace">lutff_0/in_1</span>;
and the <span style="font-family:monospace">CLKHFEN</span> input connects through input <span style="font-family:monospace">lutff_7/in_3</span> of the same tile.<br/>
The <span style="font-family:monospace">CLKHF</span> output of SB_HFOSC is connected to both IPConnect tile (0, 28) output <span style="font-family:monospace">slf_op_7</span> and to the <span style="font-family:monospace">padin</span>
of <span style="font-family:monospace">glb_netwk_4</span>.</p>
<p>Configuration bit <span style="font-family:monospace">CLKHF_DIV[1]</span> maps to DSP1 tile (0, 16) config bit <span style="font-family:monospace">CBIT_4</span>, and
<span style="font-family:monospace">CLKHF_DIV[0]</span> maps to DSP1 tile (0, 16) config bit <span style="font-family:monospace">CBIT_3</span>.</p>
<h3>SB_LFOSC</h3>
<p>The <span style="font-family:monospace">CLKLFPU</span> input connects through IPConnect tile (25, 29) input <span style="font-family:monospace">lutff_0/in_1</span>;
and the <span style="font-family:monospace">CLKLFEN</span> input connects through input <span style="font-family:monospace">lutff_7/in_3</span> of the same tile.<br/>
The <span style="font-family:monospace">CLKLF</span> output of SB_LFOSC is connected to both IPConnect tile (25, 29) output <span style="font-family:monospace">slf_op_0</span> and to the <span style="font-family:monospace">padin</span>
of <span style="font-family:monospace">glb_netwk_5</span>.</p>
<p>SB_LFOSC has no configuration bits.</p>
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