Pseudo-random Number Generator

You can't.

If the number is out of range, discard it and request another until you get one in range.

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If the number is out of range, discard it and request another until you get one in range.

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This way an undefinite number of cycles is possibly required before you get a valid result.

If you can't allow this, because you need the random number immediately, you must implement a different solution.

If you don't bother the indipendence between successive pseudo-random numbers, you can simply feed the LFSR output to a modulo 200 adder: you sum the previous number to the LFSR result, divide by 200 and take the remainder, which is actually a pseudo random number uniformly distributed between 0 and 199.

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Infinite is an exaggeration :-) Especially if the source is an LFSR.

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Infact I said undefinite, not infinite.

I mean it could require one cycle (in about 80% of cases), two retries (16%), three (3.2%, right?) and so on.

In theory, you need to change your lfsr_out to the range of 0 to 1 (1 not included) and then scale it by (limit + 1). In your 8-bit case:

wire [15:0] temp = lfsr_out * 16'd201;

wire [7:0] result = temp [15:8];

lfsr_out is the output of your LFSR and result is what you are looking for.

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In theory, you need to change your lfsr_out to the range of 0 to 1 (1 not included) and then scale it by (limit + 1). In your 8-bit case:

wire [15:0] temp = lfsr_out * 16'd201;

wire [7:0] result = temp [15:8];

lfsr_out is the output of your LFSR and result is what you are looking for.

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This way you'll get a non uniform distribution, namely some values would be much more frequent than others, expecially if LFSR output range is not a lot bigger than the desired range. Extending the LFSR length would help improving the distribution.

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Yes, it does rather depend on what sort of random numbers you want!

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one other method is to get your values in software(e.g. matlab) of any range you choose then store them in LUT and run it from there.

As such you can choose whatever type of random values are available in the tool.