78 lines
2.7 KiB
Markdown
78 lines
2.7 KiB
Markdown
# Examples_README
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## Example_1
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The goal of this example is just to make a first step into the software. The .blif contains only an inverter.
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The .xml is currently on <layout auto="1.0"/> which means that the size depends on the .blif. Since the .blif is
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almost empty, only 1 CLB will be generated.
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<img src="https://github.com/LNIS-Projects/OpenFPGA/blob/master/examples/figures/example_1.png" alt="Example_1_FPGA" width="80%">
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Schematic of the FPGA generated during example_1.
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The CLB integrates a 4-inputs LUT, a FF and a MUX.
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---
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**Things to understand in this example**
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Everything won't be explained in detail but few important structures (some common with the VPR project) are to be explained in order to build good architectures.
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```xml
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<architecture>
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<models>
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... add models such as the io pads.
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</models>
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<spice_settings>
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... all tech and spice parameters are defined here.
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<module_spice_models>
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... define the Basic Elements of the architecture and the modules that cannot
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be generated (i.e. the Flip-Flop) but need to be called.
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</module_spice_models>
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</spice_settings>
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<cblocks>
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... complex blocks
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<complexblocklist>
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... here we define the hierarchy of the primitive blocks and interconnect them
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together
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<pb_type>
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... defines the primitive block
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</pb_type>
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<interconnect>
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...
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</interconnect>
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</complexblocklist>
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</cblocks>
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</architecture>
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```
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---
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## Example_2
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Example_2's goal is to introduce the slices, the interconnections which can be generated from it and the manual mode of the layout.
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In this case, we generate a 3x3 FPGA with 4 slices. The LUTs are 6-inputs ones similarly to the ones used in the industry.
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There is a feedback-loop from the output of the slices to the input MUXs
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{:height="80%" width="80%"}
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Schematic showing the CLB generated in this example.
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---
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**Things to understand in this example**
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```xml
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<layout width="3" height="3"/> <!-- Manual mode of the layout allowing us to choose the number of CLBs -->
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<complete name="crossbar" input="clb.I fle[3:0].out" output="fle[3:0].in" spice_model_name="mux_2level">
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<!-- Defines how we apply the feedback on the inputs of the slices -->
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<delay_constant max="53.44e-12" in_port="clb.I" out_port="fle[3:0].in" />
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<delay_constant max="53.44e-12" in_port="fle[3:0].out" out_port="fle[3:0].in" />
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</complete>
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```
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{:height="80%" width="80%"}
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