Forums

"Random" Circuit Needed.

Started by Jim Thompson April 1, 2015
On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >> >>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>> wrote: >>>> >>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>> >>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>> twist... >>>>>>>> >>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>> >>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>> >>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>> device in my PSpice library. >>>>>>>> >>>>>>>> Thanks in advance. >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>>> >>>>>>> >>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>> >>>>>> I just need semi-random enough to test a fast AGC. >>>>>> >>>>>> ...Jim Thompson >>>>> >>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>the bias point to continually drift high. >>>> >>>> I was wondering about that myself... I'll see if there's a cure. >>> >>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>> >>>not that i'd want to build it using 74LS logic. >> >>--- >>But, if you had to, what would it look like, schematic-wise? >> >>John Fields > ><smirk>:-} > > ...Jim Thompson
--- Amazing, isn't it? Idiots with opinions post their garbage as if it was holy but post no evidence to support their claims. John Fields
On 4/15/2015 7:38 PM, John Fields wrote:
> On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >> On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >> <jfields@austininstruments.com> wrote: >> >>> On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>> >>>> On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>> wrote: >>>>> >>>>>> On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>> >>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>> >>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>> twist... >>>>>>>>> >>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>> >>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>> >>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>> device in my PSpice library. >>>>>>>>> >>>>>>>>> Thanks in advance. >>>>>>>>> >>>>>>>>> ...Jim Thompson >>>>>>>>> >>>>>>>> >>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>> >>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>> >>>>>>> ...Jim Thompson >>>>>> >>>>>> there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>> 'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>> appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>> the bias point to continually drift high. >>>>> >>>>> I was wondering about that myself... I'll see if there's a cure. >>>> >>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>> >>>> not that i'd want to build it using 74LS logic. >>> >>> --- >>> But, if you had to, what would it look like, schematic-wise? >>> >>> John Fields >> >> <smirk>:-} >> >> ...Jim Thompson > --- > Amazing, isn't it? > > Idiots with opinions post their garbage as if it was holy but post > no evidence to support their claims.
I don't know that Jim is an idiot, but I'm not sure this formula is very useful to implement in logic easily. The multiply is not too bad and the addition is easy. But the modulo operation by 2^16+1 is downright hard. I think that is why he is smirking. He knows this is not very practical... BTW, I did a quick search to find the method of extending an LFSR to cover the full range of 0 to 2^N values... http://www.xilinx.com/support/documentation/application_notes/xapp052.pdf Seems he detects the state with N-1 ones and inverts the output. So for a 16 bit register this requires decoding 15 bits. But for small length LFSRs this is very practical. -- Rick
On Wed, 15 Apr 2015 18:38:49 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >><jfields@austininstruments.com> wrote: >> >>>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>> >>>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>> wrote: >>>>> >>>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>> >>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>> >>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>> twist... >>>>>>>>> >>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>> >>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>> >>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>> device in my PSpice library. >>>>>>>>> >>>>>>>>> Thanks in advance. >>>>>>>>> >>>>>>>>> ...Jim Thompson >>>>>>>>> >>>>>>>> >>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>> >>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>> >>>>>>> ...Jim Thompson >>>>>> >>>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>the bias point to continually drift high. >>>>> >>>>> I was wondering about that myself... I'll see if there's a cure. >>>> >>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>> >>>>not that i'd want to build it using 74LS logic. >>> >>>--- >>>But, if you had to, what would it look like, schematic-wise? >>> >>>John Fields >> >><smirk>:-} >> >> ...Jim Thompson >--- >Amazing, isn't it? > >Idiots with opinions post their garbage as if it was holy but post >no evidence to support their claims. > >John Fields
Lot of that going around here... particularly from the one whose lame retort is always, "Design any good electronics lately? Thought not." ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Thu, 16 Apr 2015 09:17:29 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Wed, 15 Apr 2015 18:38:49 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>><jfields@austininstruments.com> wrote: >>> >>>>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>> >>>>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>> wrote: >>>>>> >>>>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>> >>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>> >>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>> twist... >>>>>>>>>> >>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>> >>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>> >>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>> device in my PSpice library. >>>>>>>>>> >>>>>>>>>> Thanks in advance. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>>> >>>>>>>>> >>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>> >>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>> >>>>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>the bias point to continually drift high. >>>>>> >>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>> >>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>> >>>>>not that i'd want to build it using 74LS logic. >>>> >>>>--- >>>>But, if you had to, what would it look like, schematic-wise? >>>> >>>>John Fields >>> >>><smirk>:-} >>> >>> ...Jim Thompson >>--- >>Amazing, isn't it? >> >>Idiots with opinions post their garbage as if it was holy but post >>no evidence to support their claims. >> >>John Fields > >Lot of that going around here... particularly from the one whose lame >retort is always, "Design any good electronics lately? Thought not." > > ...Jim Thompson
These are electronics newsgroups. We do seem to have a faction of ancient cackling farts who only want to gossip and whine about personalities, and drone out insults, and haven't touched a soldering iron in years, or decades. Decide where you want to stand. Are Fields and Sloman the people you want to be allied with? Excuse me, I have some electronics stuff to do. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Thu, 16 Apr 2015 09:17:29 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Wed, 15 Apr 2015 18:38:49 -0500, John Fields >><jfields@austininstruments.com> wrote: >> >>>On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>>><jfields@austininstruments.com> wrote: >>>> >>>>>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>> >>>>>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>>> wrote: >>>>>>> >>>>>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>>> >>>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>>> >>>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>>> twist... >>>>>>>>>>> >>>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>>> >>>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>>> >>>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>>> device in my PSpice library. >>>>>>>>>>> >>>>>>>>>>> Thanks in advance. >>>>>>>>>>> >>>>>>>>>>> ...Jim Thompson >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> >>>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>>> >>>>>>>>> ...Jim Thompson >>>>>>>> >>>>>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>>the bias point to continually drift high. >>>>>>> >>>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>>> >>>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>>> >>>>>>not that i'd want to build it using 74LS logic. >>>>> >>>>>--- >>>>>But, if you had to, what would it look like, schematic-wise? >>>>> >>>>>John Fields >>>> >>>><smirk>:-} >>>> >>>> ...Jim Thompson >>>--- >>>Amazing, isn't it? >>> >>>Idiots with opinions post their garbage as if it was holy but post >>>no evidence to support their claims. >>> >>>John Fields >> >>Lot of that going around here... particularly from the one whose lame >>retort is always, "Design any good electronics lately? Thought not." >> >> ...Jim Thompson > >These are electronics newsgroups. We do seem to have a faction of >ancient cackling farts who only want to gossip and whine about >personalities, and drone out insults, and haven't touched a soldering >iron in years, or decades. > >Decide where you want to stand. Are Fields and Sloman the people you >want to be allied with? > >Excuse me, I have some electronics stuff to do.
Oh, my! Did you think I meant _you_ ?>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 4/16/2015 2:16 PM, Jim Thompson wrote:
> On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin > <jlarkin@highlandtechnology.com> wrote: > >> On Thu, 16 Apr 2015 09:17:29 -0700, Jim Thompson >> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>> On Wed, 15 Apr 2015 18:38:49 -0500, John Fields >>> <jfields@austininstruments.com> wrote: >>> >>>> On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >>>> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> >>>>> On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>>>> <jfields@austininstruments.com> wrote: >>>>> >>>>>> On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>> >>>>>>> On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>>>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>>>> >>>>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>>>> >>>>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>>>> twist... >>>>>>>>>>>> >>>>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>>>> >>>>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>>>> >>>>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>>>> device in my PSpice library. >>>>>>>>>>>> >>>>>>>>>>>> Thanks in advance. >>>>>>>>>>>> >>>>>>>>>>>> ...Jim Thompson >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>>>> >>>>>>>>>>> Cheers >>>>>>>>>>> >>>>>>>>>>> Phil Hobbs >>>>>>>>>> >>>>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>> >>>>>>>>> there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>>> 'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>>> appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>>> the bias point to continually drift high. >>>>>>>> >>>>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>>>> >>>>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>>>> >>>>>>> not that i'd want to build it using 74LS logic. >>>>>> >>>>>> --- >>>>>> But, if you had to, what would it look like, schematic-wise? >>>>>> >>>>>> John Fields >>>>> >>>>> <smirk>:-} >>>>> >>>>> ...Jim Thompson >>>> --- >>>> Amazing, isn't it? >>>> >>>> Idiots with opinions post their garbage as if it was holy but post >>>> no evidence to support their claims. >>>> >>>> John Fields >>> >>> Lot of that going around here... particularly from the one whose lame >>> retort is always, "Design any good electronics lately? Thought not." >>> >>> ...Jim Thompson >> >> These are electronics newsgroups. We do seem to have a faction of >> ancient cackling farts who only want to gossip and whine about >> personalities, and drone out insults, and haven't touched a soldering >> iron in years, or decades. >> >> Decide where you want to stand. Are Fields and Sloman the people you >> want to be allied with? >> >> Excuse me, I have some electronics stuff to do. > > Oh, my! Did you think I meant _you_ ?>:-}
LOL! The part I find very amusing is the "ancient cackling fart" who is whining about the other "ancient cackling farts" whining. LOL! -- Rick
On Thu, 16 Apr 2015 11:16:13 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > >>On Thu, 16 Apr 2015 09:17:29 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Wed, 15 Apr 2015 18:38:49 -0500, John Fields >>><jfields@austininstruments.com> wrote: >>> >>>>On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> >>>>>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>>>><jfields@austininstruments.com> wrote: >>>>> >>>>>>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>> >>>>>>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>>>> wrote: >>>>>>>> >>>>>>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>>>> >>>>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>>>> >>>>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>>>> twist... >>>>>>>>>>>> >>>>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>>>> >>>>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>>>> >>>>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>>>> device in my PSpice library. >>>>>>>>>>>> >>>>>>>>>>>> Thanks in advance. >>>>>>>>>>>> >>>>>>>>>>>> ...Jim Thompson >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>>>> >>>>>>>>>>> Cheers >>>>>>>>>>> >>>>>>>>>>> Phil Hobbs >>>>>>>>>> >>>>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>> >>>>>>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>>>the bias point to continually drift high. >>>>>>>> >>>>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>>>> >>>>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>>>> >>>>>>>not that i'd want to build it using 74LS logic. >>>>>> >>>>>>--- >>>>>>But, if you had to, what would it look like, schematic-wise? >>>>>> >>>>>>John Fields >>>>> >>>>><smirk>:-} >>>>> >>>>> ...Jim Thompson >>>>--- >>>>Amazing, isn't it? >>>> >>>>Idiots with opinions post their garbage as if it was holy but post >>>>no evidence to support their claims. >>>> >>>>John Fields >>>
>>>Lot of that going around here... particularly from the one whose lame >>>retort is always, "Design any good electronics lately? Thought not." >>> >>> ...Jim Thompson
>> >>These are electronics newsgroups. We do seem to have a faction of >>ancient cackling farts who only want to gossip and whine about >>personalities, and drone out insults, and haven't touched a soldering >>iron in years, or decades. >> >>Decide where you want to stand. Are Fields and Sloman the people you >>want to be allied with? >> >>Excuse me, I have some electronics stuff to do. > >Oh, my! Did you think I meant _you_ ?>:-} > > ...Jim Thompson
You directly quoted my "lame retort." -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Thu, 16 Apr 2015 01:07:08 -0400, rickman <gnuarm@gmail.com>
wrote:

>On 4/15/2015 7:38 PM, John Fields wrote: >> On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>> On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>> <jfields@austininstruments.com> wrote: >>> >>>> On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>> >>>>> On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>> wrote: >>>>>> >>>>>>> On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>> >>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>> >>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>> twist... >>>>>>>>>> >>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>> >>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>> >>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>> device in my PSpice library. >>>>>>>>>> >>>>>>>>>> Thanks in advance. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>>> >>>>>>>>> >>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>> >>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>> >>>>>>> there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>> 'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>> appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>> the bias point to continually drift high. >>>>>> >>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>> >>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>> >>>>> not that i'd want to build it using 74LS logic. >>>> >>>> --- >>>> But, if you had to, what would it look like, schematic-wise? >>>> >>>> John Fields >>> >>> <smirk>:-} >>> >>> ...Jim Thompson >> --- >> Amazing, isn't it? >> >> Idiots with opinions post their garbage as if it was holy but post >> no evidence to support their claims. > >I don't know that Jim is an idiot,
--- The reference to idiocy wasn't pointing to Jim, it was pointed at Betts. ---
> but I'm not sure this formula is very >useful to implement in logic easily.
--- You echo my point. ---
>The multiply is not too bad and >the addition is easy. But the modulo operation by 2^16+1 is downright >hard. I think that is why he is smirking. He knows this is not very >practical...
--- You have a remarkable grasp of the obvious. ---
>BTW, I did a quick search to find the method of extending an LFSR to >cover the full range of 0 to 2^N values... > >http://www.xilinx.com/support/documentation/application_notes/xapp052.pdf > >Seems he detects the state with N-1 ones and inverts the output. So for >a 16 bit register this requires decoding 15 bits. But for small length >LFSRs this is very practical.
--- If you need the extra state, then even for huge counters the practicality fades into insignificance. John Fields
On 4/16/2015 4:46 PM, John Fields wrote:

> If you need the extra state, then even for huge counters the > practicality fades into insignificance. > > John Fields >
I'm not sure what that means. Practicality is *always* an issue that needs consideration. The primary point of LFSRs is that they can be built to run quickly and take of little space because of the minimal logic requirements. If you throw that away you can start looking at a much larger field of contenders. -- Rick
On Thu, 16 Apr 2015 09:17:29 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Wed, 15 Apr 2015 18:38:49 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>><jfields@austininstruments.com> wrote: >>> >>>>On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>> >>>>>On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>> wrote: >>>>>> >>>>>>>On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>> >>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>> >>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>> twist... >>>>>>>>>> >>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>> >>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>> >>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>> device in my PSpice library. >>>>>>>>>> >>>>>>>>>> Thanks in advance. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>>> >>>>>>>>> >>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>> >>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>> >>>>>>>there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>the bias point to continually drift high. >>>>>> >>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>> >>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>> >>>>>not that i'd want to build it using 74LS logic. >>>> >>>>--- >>>>But, if you had to, what would it look like, schematic-wise? >>>> >>>>John Fields >>> >>><smirk>:-} >>> >>> ...Jim Thompson >>--- >>Amazing, isn't it? >> >>Idiots with opinions post their garbage as if it was holy but post >>no evidence to support their claims. >> >>John Fields > >Lot of that going around here... particularly from the one whose lame >retort is always, "Design any good electronics lately? Thought not." > > ...Jim Thompson
--- Indeed, and in the end that retort is never a genuine invitation to share, it's always just a diversion to shift the focus of the thread away from a question which can't be answered without loss of face or a statement which can't be refuted. John Fields