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Sela
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Simulink HDL coder Shift register SIPO

Asked by Sela
on 13 Nov 2017
Latest activity Answered by David
on 18 May 2018
Hi everybody,
I work on model Simulink which has to generate VHDL code with the command HDL coder.
My problem is on the last step of my model.
I wish to make a shift register SIPO so with an input (1,1) and an output (1,8). My input takes new value at each clock, I would concatened all this values in one.
I have already tried with a lot of Simulink block : HDL FIFO, ShiftRegister 1 by 64, MATLAB function, bit concate... but for this instance, I have not find solution.
Could you please send me a example of ShiftRegister SIPO at 8 bits please?
Thanks for your help,
Sela

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1 Answer

Answer by David
on 18 May 2018

The attached is a simulink testbench for the configurable SIPO shift register.
function [update_out, po] = SIPO(update_in, si)
%#codegen
num_bits = 8; % Number of bits to output
persistent parallel_out ...
regout ...
count_bits % Count the bits being output
if isempty(parallel_out)
parallel_out = fi(0,0,num_bits,0);
regout = fi(0,0,num_bits,0);
count_bits = fi(0,0,ceil(log2(num_bits))+1,0);
end
po = fi(0,0,num_bits,0); % Parallel output of width "num_bits"
po(:) = regout; % Register output
update_out = fi(0,0,1,0); % binary update output.
if update_in == 1
% The actual shift register here.
% join the old with the new
% by dropping the MSB and keeping the bits below this to the LSB.
% and appending the si input to the LSB.
parallel_out(:) = ...
bitconcat(... % join the following two fixed point values
bitsliceget( parallel_out , num_bits-1 , 1 ) ,... get one less than MSB downto the LSB
fi(si,0,1,0));
if count_bits >= num_bits
regout(:) = parallel_out;
update_out = fi(1,0,1,0); % There has been an output
count_bits(:) = 0;
else
count_bits(:) = count_bits + 1;
end
end

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