Lookup table

175

01:40:05

This is a simple lookup table at two input.
The function saved in the 4 bit "sram" is a x-or, but we can save every function at two input.
There is a mux whit two selection input.
Sorry for my english.

Questa è una semplice lut (lookup table) ovvero tabella di consultazione, a due ingressi di selezione.
La lut sfrutta 2^n celle sram per bit per salvare funzioni ad n bit. Il dato viene prelevato col mux grazie agli ingressi di selezione.
L'utilità sta nella versatilità del circuito il quale è capace di implementare funzioni anche più complesse in modo elastico, scrivendone solo la funzione nella sram. 
Ho implementato una x-or a 2 bit a scopo illustrativo. Per mostrare la potenza della lut bisogna immaginare a quanto può essere complicato il circuito a crescere del n di bit della funzione.
La lut è alla base dei blocchi logici (clb) delle fpga.

published 9 years ago

Redstone_guy

1 year ago

Translation (from Italian): This is a simple lut (lookup table) or consultation table, with two selection inputs. The lut uses 2^n sram cells per bit to save functions to n bits. The data is taken with the mux thanks to the selection inputs. The usefulness lies in the versatility of the circuit which is capable of implementing even more complex functions in an elastic way, writing only the function in the sram. I implemented a 2-bit x-or for illustrative purposes. To show the power of the lut you have to imagine how complicated the circuit can be to grow by the n of bits of the function. The lut is the basis of the logical blocks (clb) of the fpga.

Redstone_guy

1 year ago

In EveryCircuit, however, there are currently no static memory components; the moment the simulation is stopped, all the analog and digital signals saved to the components are lost, meaning that all the digital components use dynamic memory, that is, requires constant power (or in this case, simulation running) to keep its data

Redstone_guy

1 year ago

If you want to see what a 4-bit LUT pushed to the limits looks like, feel free to try: http://everycircuit.com/circuit/6315106958573568

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