pbw@cbosgd.UUCP (Paul Westerfield) (01/08/84)
I need a good design for a HARDWARE random number generator to go into an 8-bit parallel port (TTL). Actually a simple one bit generator with TTL output and no need to adjust weighting would do. The only design I've seen gets '1' or '0' heavy after awhile, and needs adjustment. Also nice would be a source of CHEAP S-100 bare boards (perf board for wire wrapping). The lowest price I've seen is $45.00 new, and I haven't been able to find used. Reply via mail. Thanks. P.B. Westerfield cbosgd!pbw
davis@hplabs.UUCP (Jim Davis) (01/09/84)
With reference to a hardware random number generator (NOT a Pseudo-random number generator): Any generator that gets 1 or 0 heavy after a while can be easily fixed. Write a routine that when a 0 or a 1 is desired, reads in two values. Let 10 => 1, 01 => 0, and 11 or 00 mean to try again. Too many try agains mean that your generator has died. If the original generator is powered from true noise (no great coefficient between alternate terms) then this will avoid becomming 1 or 0 heavy. -- Jim Davis (James W Davis) ...!ucbvax!hplabs!davis davis.HP-Labs@Rand-Relay ----------------------------------------------------------------
rpw3@fortune.UUCP (01/12/84)
#R:cbosgd:-80800:fortune:12300010:000:1114
fortune!rpw3 Jan 12 02:09:00 1984
If you just need "random" noise, a sufficiently fast TTL clock will
appear random, especially if you use a pseudo-random method of picking
bits and of picking polarity.
A more complex (but not necessarily better) method is to run a D/A
into the "+" side of a comparator, run the output to a TTL Schmitt
trigger, which goes to you PIO port and... back to the "-" side of the
comparator. The comparator/Schmitt will oscillate like a banshee
(due to the hysteresis in the Schmitt trigger), and the D/A can be used
to adaptively bias the ratio of 1's to 0's.
The "most" random source I have seen used a VHF noise diode (yes they
make them deliberately noisy) in an analog version of the preceeding
circuit. That is, the (properly biased) noise diode goes into the
comparator and then to a Schmitt trigger, which goes to the sampler and...
back to an integrator which averages the 1/0 ratio and feeds a D.C.
voltage to the comparator.
Good luck.
Rob Warnock
UUCP: {sri-unix,amd70,hpda,harpo,ihnp4,allegra}!fortune!rpw3
DDD: (415)595-8444
USPS: Fortune Systems Corp, 101 Twin Dolphins Drive, Redwood City, CA 94065malcolm@ecn-ee.UUCP (01/18/84)
#R:cbosgd:-80800:ecn-ee:14600003:000:189 ecn-ee!malcolm Jan 11 00:01:00 1984 I'm not sure if this would really work, but...... A number of people have suggested that CCD memory chips make good random number generators. Malcolm Slaney Hardware Hacker