Simulink bit operations

2011 12 16
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Hi all, I wanted to ask if from a number of bits that are represented with 1 and 0 is possible to invert the ones to -1 each lets say two bits? Thanks in advance.

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Fangjun Jiang
Fangjun Jiang 2011-12-17
Not clear to me what do you mean by "from a number of bits" and "to invert the ones to -1 each lets say two bits". Are you saying that if you have an inputs of 10 bits, six 1s and four 0s, alternate randomly, you want to invert the first two 1s into -1?
Raldi
Raldi 2012-1-13
basicaly i was trying to create an ami nrz line code, i think flip flops is the only way to do that. I havent finish it yet though.

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Paulo Silva
Paulo Silva 2011-12-16

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[1 0]------>Gain(-1)----->[-1 0]
Use the Gain block and define that gain as -1

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Raldi
Raldi 2011-12-16
but wont this transform all ones to -1?
i want for excmple [1 1 0 1]---->[1 -1 0 1]
Paulo Silva
Paulo Silva 2011-12-16
Yes you are right, it's something easy to do in MATLAB but not in Simulink, maybe someone can help you with a better solution
Paulo Silva
Paulo Silva 2011-12-16
For that example you can try the Product block and use element wise operations
[1 1 0 1]----->Product>----[1 -1 0 1]
[1 -1 1 1]---->_______
Raldi
Raldi 2011-12-16
Still it wont work as i am using a bernoulli generator so i dont know the number of the bits. I think the best way to do it is using logical excpresions and timers, but i havent figured out how yet.
Walter Roberson
Walter Roberson 2011-12-16
How many bits per time sample is your generator producing? If it is one bit per time sample then perhaps use a step function that flips between -1 and 1 every two steps.
Walter Roberson
Walter Roberson 2011-12-16
Ah, instead of a step function, you could perhaps use a Repeating Sequence block, as mentioned at http://www.mathworks.com/matlabcentral/answers/15874-hi-all-i-am-having-a-difficulty-in-switching-a-signal-i-need-a-switch-in-simulink-that-must-be-on
Raldi
Raldi 2012-1-13
I was thinking more of using a flip flop as it has memmory, The general idea was to create a simple ami-nrz line code.

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Raldi
Raldi
2011-12-16

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