How to initialise look-up tables?

[ravi_meghadri]

My design is having a memory unit and it has to act as look-up table. How to initialise it at the start up. It is of size 256 x 20 bits.

 

[rberek]

Well, there are several ways to initialize it:

1) If the LUT holds data that never changes, your ASIC technology might include ROM structures, in which case you could use a ROM as the look up table, and the manufacturer's ASIC process will have a method to define the contents during design.

2) you could write your RTL to include an initialization sequence that, after reset is deasserted, your functional block writes the LUT data into the memory. This is especially useful if the LUT holds a repeating or deterministic pattern. But, you can still define any pattern you like.

3) If the LUT is meant to be reconfigurable, then you could load it via a processor interface during your chip's init sequence.

Just a few suggestions.

r.b.

 

[fpga_asic_designer]

can you do this?

reg [19:0] lut [255:0];

generate
for ...
always@(posedge iCLK or posedge iRST)
begin
if (iRST == 1)
lut = 'h0;
else
.....
end
endgenerate

My design is having a memory unit and it has to act as look-up table. How to initialise it at the start up. It is of size 256 x 20 bits.