On Wed, 17 Jan 1996, Timothy L. Nali wrote:
Hi all
For a class project, I will be designing a VLSI cmos chip to generate truly random numbers (The chip will be fabricated). I'm limited to a 2-micron standard cmos technology (no fancy BiCMOS, MISC, or anthing else). The most promising design I've seen so far (that I can actually do) is based on clocking a D flip-flop in the following way:
----- 8Khz clock ------ | |----- Random output | | | | (sloppy) slow clock ---- |> | | | -----
you can enhance the thermal stability with a temperature control scheme. and you can virtually eliminate voltage problems with separate regulation. use a digital oscillator and clean up the edges. would you not be better off for true randomness to use a) a > 8Mz clock, and b) to chain the output of one into the control gate of a second? I think that gives you better spectral distribution presuming you use a second clock frequency. unlike most, I am still of the opinion that digital means of generating this should be more uniform. otherwise, use a high-frequency diode, analog weight the curve, analog high-pass it, sample it, and go for it. or take several TV stations, phase and mix the horizontal scans, etc. --but I thought this was a digital project for CMOS --actually CMOS can generate white noise, but you probably will end up with a DSP on your chip! biasing should be controllable with edge control. However, all of above needs to be bench tested for the practical results --keeping in mind measuring randomness of segments of a bit stream are "impossible" --thoroughly frustating. another schema is to play the old enigma game of lining up the spinning wheels -that works digitally, the gates on CMOS are not too hairy -the question is how many wheels and their relative rotation (including direction)? and, how many levels? how much real estate do you have at 2u? I ask because the use of the rotating wheels has been an old project I dumped since fab was far to expensive in the 70s --but it has held my interest. there has also been a thorough trashing or thrashing of RNG recently which should be in the archives.
I'd also appreciate any other suggestions or advice you have on RNGs.
Thanks in advance.
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