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{{┌───────────────────────────────────────────┬────────────────┬───────────────────────────────────┬───────────────┐│ Real Random v1.2 │ by Chip Gracey │ Copyright (c) 2007 Parallax, Inc. │ 23 March 2007 │├───────────────────────────────────────────┴────────────────┴───────────────────────────────────┴───────────────┤│ ││ This object generates real random numbers by stimulating and tracking CTR PLL jitter. It requires one cog and ││ at least 20MHz. ││ │├────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤│ Background and Detail: ││ ││ A real random number is impossible to generate within a closed digital system. This is because there are no ││ reliably-random states within such a system at power-up, and after power-up, it behaves deterministically. ││ Random values can only be 'earned' by measuring something outside of the digital system. │ │ ││ In your programming, you might have used 'var?' to generate a pseudo-random sequence, but found the same ││ pattern playing every time you ran your program. You might have then used 'cnt' to 'randomly' seed the 'var'. ││ As long as you kept downloading to RAM, you saw consistently 'random' results. At some point, you probably ││ downloaded to EEPROM to set your project free. But what happened nearly every time you powered it up? You were ││ probably dismayed to discover the same sequence playing each time! The problem was that 'cnt' was always ││ powering-up with the same initial value and you were then sampling it at a constant offset. This can make you ││ wonder, "Where's the end to this madness? And will I ever find true randomness?". │ │ ││ In order to have real random numbers, either some external random signal must be input, or some analog system ││ must be used to generate random noise which can be measured. We're in luck here, because it turns out that the ││ Propeller does have sufficiently-analog subsystems which can be exploited for this purpose -- each cog's CTR ││ PLLs. These can be exercised internally to good effect, without any I/O activity. │ │ ││ This object
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