270 lines
8.0 KiB
Matlab
270 lines
8.0 KiB
Matlab
classdef MRDS_coding
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%MRDS implementation according to:
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% Optical Multi-Path Interference Mitigation for PAM4-IMDD Systems Using Balanced Coding
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% Journal of Lightwave Technology; 2024
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properties(Access=public)
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blocklength
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delta
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end
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methods (Access=public)
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function obj = MRDS_coding(options)
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%NAME Construct an instance of this class
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% Detailed explanation goes here
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arguments
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options.blocklength = 8;
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end
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%
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fn = fieldnames(options);
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for n = 1:numel(fn)
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try
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obj.(fn{n}) = options.(fn{n});
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end
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end
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end
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function process(~)
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error("MRDS_coding has no process function. Use .encode(signal) and .dc_remove(signal) and .decode(signal)");
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end
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function signalclass_out = encode(obj,signalclass_in)
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data_in = signalclass_in.signal';
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if mean(unique(data_in)) < 0.01 % --> check for bipolar
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data_in = int32(data_in.*sqrt(5));
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data_in = double(data_in);
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else % unipolar
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data_in = int32(data_in.*sqrt(5)*2-3); % make bipolar [-3, -1, 1, 3]
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data_in = double(data_in);
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end
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data_out = obj.mrds_encoding(data_in, obj.blocklength);
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data_out = data_out./sqrt(5); % normalized to Power=1
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signalclass_in.signal = data_out';
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% append to logbook
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lbdesc = ['MRDS Coded'];
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signalclass_in = signalclass_in.logbookentry(lbdesc);
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% write to output
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signalclass_out = signalclass_in;
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end
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function signalclass_out = decode(obj,signalclass_in)
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data_in = signalclass_in.signal';
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if mean(unique(data_in)) < 0.01 % --> check for bipolar
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data_in = int32(data_in.*sqrt(5));
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data_in = double(data_in);
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else % unipolar
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data_in = int32(data_in.*sqrt(5)*2-3); % make bipolar [-3, -1, 1, 3]
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data_in = double(data_in);
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end
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data_oh = obj.oh_decider(data_in, obj.blocklength); % decider for overhead
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data_out = obj.mrds_decoding(data_oh, obj.blocklength);
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data_out = data_out./sqrt(5); % normalized to Power=1
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signalclass_in.signal = data_out';
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% append to logbook
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lbdesc = ['MRDS Coded'];
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signalclass_in = signalclass_in.logbookentry(lbdesc);
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% write to output
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signalclass_out = signalclass_in;
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end
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function signalclass_out = dc_remove(obj,signalclass_in,options)
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arguments
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obj
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signalclass_in
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options.oversampling_factor = 1;
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end
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signalclass_in.signal = obj.dcr(signalclass_in.signal, obj.blocklength, options.oversampling_factor);
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% append to logbook
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lbdesc = ['MRDS DC Removed'];
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signalclass_in = signalclass_in.logbookentry(lbdesc);
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% write to output
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signalclass_out = signalclass_in;
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end
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end
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methods (Access=private)
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% Cant be seen from outside! So put all your functions here that can/
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% shall not be called from outside
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Function 1 - encoding
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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function [data_out] = mrds_encoding(~,data_in, blocklength)
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% data_in: bipolar PAM4 sequence with levels [-3, -1, 1, 3]
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% with length power of two
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% blocklength: power of two <= length of data_in
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oh_length = log2(blocklength);
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data_out = zeros(1,length(data_in)+length(data_in)/blocklength*oh_length);
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l = 0;
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for j = 1:blocklength:length(data_in)
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data = data_in(j:j+blocklength-1);
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z_N = zeros(1,blocklength); % RDS
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z_rds = 0;
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for i = 1:blocklength
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z_rds = z_rds + data(i);
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z_N(i) = z_rds;
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end
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z = z_rds/2; % find inversion point k
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k = find(z_N == z);
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[~, index] = min(abs(blocklength/2 - k));
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k = k(index);
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if isempty(k) == 1
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k = blocklength;
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end
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if k == blocklength
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overhead = ones(1,oh_length)*3;
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else
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overhead = (decimalToBinaryVector(k-1,log2(blocklength))-0.5)*6; % calculate OH
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data(k+1:end) = data(k+1:end)*(-1); % invert
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end
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data_oh = [data overhead];
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data_out(l*(blocklength+oh_length)+1:(l+1)*(blocklength+oh_length)) = data_oh;
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l = l+1;
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end
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end
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Function 2 - decoding
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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function [data_out] = mrds_decoding(~,data_in, blocklength)
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oh_length = log2(blocklength);
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data_out = zeros(1,length(data_in)-length(data_in)/(blocklength+oh_length)*oh_length);
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l = 1;
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for j = 1:(blocklength+oh_length):length(data_in)
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data = data_in(j:j+blocklength+oh_length-1);
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overhead = data(blocklength+1:end)/6+0.5;
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k = binaryVectorToDecimal(overhead)+1;
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if k == blocklength
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data = data(1:blocklength);
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else
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data = data(1:blocklength);
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data(k+1:end) = data(k+1:end)*(-1); % invert
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end
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data_out(l:l+blocklength-1) = data;
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l = l+blocklength;
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end
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end
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Function 3 - decider for overhead values
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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function [data_out] = oh_decider(~,data_in, blocklength)
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oh_length = log2(blocklength);
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threshold = 0;
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data_out = data_in;
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for j = 1:length(data_in)/(blocklength+oh_length)
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for k = 1:oh_length
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if data_in(j*blocklength+(j-1)*oh_length+k) >= threshold
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data_out(j*blocklength+(j-1)*oh_length+k) = 3;
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else
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data_out(j*blocklength+(j-1)*oh_length+k) = -3;
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end
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end
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end
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end
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Function 4 - matched DC removal (DCR)
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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function [data_out] = dcr(~,data_in, blocklength, oversampling_factor)
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oh_length = log2(blocklength);
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winlength = blocklength+oh_length;
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if oversampling_factor > 1
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winlength = winlength*oversampling_factor;
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end
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for j = 1:winlength:length(data_in)
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try
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data = data_in(j:j+winlength-1);
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rmean = mean(data);
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data_out(j:j+winlength-1) = data - rmean;
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catch
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if j+winlength > length(data_in)
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data = data_in(j:length(data_in));
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else
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error('indice problem.')
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end
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rmean = mean(data);
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data_out(j:length(data_in)) = data - rmean;
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end
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end
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data_out = data_out';
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end
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end
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end
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