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Messages from 159625

Article: 159625
Subject: Re: VHDL, how to convert sensor data to Q15
From: rickman <gnuarm@gmail.com>
Date: Sat, 21 Jan 2017 17:25:20 -0500
Links: << >>  << T >>  << A >>
On 1/21/2017 10:58 AM, abirov@gmail.com wrote:
> Sensor data length is 16 bit data, value is from -32768 to 32767,i think data format represented as one highest is sign and others are integers, who can help how to convert it to Q15 data format in VHDL?
>
> Q15 like https://en.wikipedia.org/wiki/Q_(number_format) one sigh and others are fractional from -1 to 1
>
> Sensor is ADC output is 16 bit format, one sign and other integer
>
> so it need only divide ?  ADC output to 32768 ??

As others have indicated, there is no logic required to convert between 
the two formats.  Here are some links for the proposed IEEE fixed point 
arithmetic package.

http://wayback.archive.org/web/20151124101646/http://www.vhdl.org/fphdl/Fixed_ug.pdf

http://wayback.archive.org/web/20151130082614/http://vhdl.org/fphdl/fixed_pkg_c.vhdl

-- 

Rick C

Article: 159626
Subject: Re: VHDL, how to convert sensor data to Q15
From: rickman <gnuarm@gmail.com>
Date: Sat, 21 Jan 2017 17:26:40 -0500
Links: << >>  << T >>  << A >>
On 1/21/2017 5:25 PM, rickman wrote:
> On 1/21/2017 10:58 AM, abirov@gmail.com wrote:
>> Sensor data length is 16 bit data, value is from -32768 to 32767,i
>> think data format represented as one highest is sign and others are
>> integers, who can help how to convert it to Q15 data format in VHDL?
>>
>> Q15 like https://en.wikipedia.org/wiki/Q_(number_format) one sigh and
>> others are fractional from -1 to 1
>>
>> Sensor is ADC output is 16 bit format, one sign and other integer
>>
>> so it need only divide ?  ADC output to 32768 ??
>
> As others have indicated, there is no logic required to convert between
> the two formats.  Here are some links for the proposed IEEE fixed point
> arithmetic package.
>
> http://wayback.archive.org/web/20151124101646/http://www.vhdl.org/fphdl/Fixed_ug.pdf
>
>
> http://wayback.archive.org/web/20151130082614/http://vhdl.org/fphdl/fixed_pkg_c.vhdl

And you might need this one too.

http://wayback.archive.org/web/20160129055142/http://www.vhdl.org/fphdl/fixed_float_types_c.vhdl

-- 

Rick C

Article: 159627
Subject: VHDL Editors (esp. V3S)
From: thomas.entner99@gmail.com
Date: Sat, 21 Jan 2017 16:36:43 -0800 (PST)
Links: << >>  << T >>  << A >>
As X and A's integrated editors are more or less limited, I guess many peop=
le will looking for better alternatives.

The usual suspects will be Emacs (with VHDL mode) and Sigasi.

For me personally, I never really liked Emacs and found Sigasi just a bit t=
oo expensive.

So some time ago I came across V3S from www.vide-software.at. It is a quite=
 powerful and fair priced VHDL plug-in for Visual Studio (Stand-alone versi=
on with Visual Studio redistributable package also available). I could also=
 watch the progress over the last few months and I really like it.

The only drawback is the missing Linux support. However, there appears to b=
e a Linux version of "Visual Studio Code". I have not checked yet if this w=
orks together with the plug-in. Maybe someone else has?

Regards,

Thomas

P.S.: I am in no way related to V3S, just a happy user. I want to sell you =
EEBlasters, JPEG encoders and cameras at www.entner-electronics.com, howeve=
r ;-)

Article: 159628
Subject: Re: VHDL, how to convert sensor data to Q15
From: HT-Lab <hans64@htminuslab.com>
Date: Sun, 22 Jan 2017 09:24:13 +0000
Links: << >>  << T >>  << A >>
On 21/01/2017 22:26, rickman wrote:
> On 1/21/2017 5:25 PM, rickman wrote:
..
>>
>> As others have indicated, there is no logic required to convert between
>> the two formats.  Here are some links for the proposed IEEE fixed point
>> arithmetic package.
>>
>> http://wayback.archive.org/web/20151124101646/http://www.vhdl.org/fphdl/Fixed_ug.pdf
>>
>>
>>
>> http://wayback.archive.org/web/20151130082614/http://vhdl.org/fphdl/fixed_pkg_c.vhdl
>>
>
> And you might need this one too.
>
> http://wayback.archive.org/web/20160129055142/http://www.vhdl.org/fphdl/fixed_float_types_c.vhdl
>
>
Bit of extra info, I would not compile these packages yourself but use 
the ones supplied with your simulator as they are most likely tuned for 
some extra performance.

In Modelsim you can find the precompiled library in 
<install_dir>\floatfixlib and the source files in 
<install_dir>\vhdl_src\floatfixlib.

Good luck,

Hans
www.ht-lab.com

Article: 159629
Subject: Re: VHDL Editors (esp. V3S)
From: Tim Wescott <seemywebsite@myfooter.really>
Date: Sun, 22 Jan 2017 19:58:48 -0600
Links: << >>  << T >>  << A >>
On Sat, 21 Jan 2017 16:36:43 -0800, thomas.entner99 wrote:

> As X and A's integrated editors are more or less limited, I guess many
> people will looking for better alternatives.
> 
> The usual suspects will be Emacs (with VHDL mode) and Sigasi.
> 
> For me personally, I never really liked Emacs and found Sigasi just a
> bit too expensive.
> 
> So some time ago I came across V3S from www.vide-software.at. It is a
> quite powerful and fair priced VHDL plug-in for Visual Studio
> (Stand-alone version with Visual Studio redistributable package also
> available). I could also watch the progress over the last few months and
> I really like it.
> 
> The only drawback is the missing Linux support. However, there appears
> to be a Linux version of "Visual Studio Code". I have not checked yet if
> this works together with the plug-in. Maybe someone else has?
> 
> Regards,
> 
> Thomas
> 
> P.S.: I am in no way related to V3S, just a happy user. I want to sell
> you EEBlasters, JPEG encoders and cameras at www.entner-electronics.com,
> however ;-)

Try Eclipse.  They cover a huge number of languages.  A nice thing for me 
is that much of the UI is standard Eclipse, with nice extensions for 
language-awareness built in.

I'm currently using it for C/C++ development, html, and LaTeX -- and I 
have done Java with it in the past.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Article: 159630
Subject: Re: Ball-park price of Xilinx Virtex 7 FPGA?
From: john.pallazola@earthtron.com
Date: Mon, 23 Jan 2017 14:04:37 -0800 (PST)
Links: << >>  << T >>  << A >>
On Wednesday, March 28, 2012 at 1:31:41 PM UTC-4, Elam wrote:
> I understand that the price depends on the volume etc
> but I would like to know the per unit price of Virtex 7 FPGA..
> 
> Any guesses..
> 
> Thanks
> Elam.

Elam,
We can save you substantially off of the Xilinx or Avnet screen pricing on most Xilinx.
John.Pallazola@earthtron.com

Article: 159631
Subject: Re: Ball-park price of Xilinx Virtex 7 FPGA?
From: rickman <gnuarm@gmail.com>
Date: Mon, 23 Jan 2017 19:58:17 -0500
Links: << >>  << T >>  << A >>
On 3/11/2014 5:32 PM, langwadt@fonz.dk wrote:
> Den tirsdag den 11. marts 2014 22.23.36 UTC+1 skrev Jon Elson:
>> GaborSzakacs wrote:
>>
>>
>>
>>
>>
>>>
>>
>>> A quick DigiKey search showed a range of $2,583.75 (XC7VX330T-1FFG1157C)
>>
>>> to $39,452.40 (XC7V2000T-G2FLG1925E).  These won't end up in any of my
>>
>>> designs any time soon.
>>
>>>
>>
>> REALLY!  1900 balls, and all of them have to solder perfectly or the chip
>>
>> has to come off and be re-balled!  Arghhhh!  I'd LOVE to know who is
>>
>> actually USING chips that expensive.  Must be the military in those
>>
>> $500 Million airplanes.
>>
>> Jon
>
> if it does the job of an asic that would require a million dollar NRE and
> you only need 20 it's a bargain

One place I worked at used a very expensive Xilinx device (not sure just 
how bad it was, I think $1,500 in around 2000) when only 20% was being 
used.  Room for expansion in a $100,000 product.  It was test equipment 
and I think they only sold a couple of handfulls.

-- 

Rick C

Article: 159632
Subject: Re: Ball-park price of Xilinx Virtex 7 FPGA?
From: rickman <gnuarm@gmail.com>
Date: Mon, 23 Jan 2017 20:02:59 -0500
Links: << >>  << T >>  << A >>
On 4/2/2012 7:55 PM, Ed McGettigan wrote:
> On Mar 28, 10:31 am, Elam <elampoora...@gmail.com> wrote:
>> I understand that the price depends on the volume etc
>> but I would like to know the per unit price of Virtex 7 FPGA..
>>
>> Any guesses..
>>
>> Thanks
>> Elam.
>
> There are too many variables (device, package, speed grade, volume,
> delivery date, etc..) involved in pricing for any simple answer.
> Contact your local Xilinx sales rep and they would be happy to sit
> down and discuss your needs and come up with the right pricing that
> matches your situation.
> http://www.xilinx.com/company/contact/sales-reps.htm
>
> Using online pricing data for 1-10 parts today will not be reflective
> of 1K-10K pricing 18 months from now.

No only do prices vary on a lot of factors, prices are *always* cheaper 
(sometimes *much* cheaper) if you give them a design win using their new 
product line.  They barely care about new sockets using old parts, even 
one generation old.  It's all about paying for the NRE on the new 
product line.  If you are buying even just 10k per year, you can get a 
great discount typically, much better than the online prices.

-- 

Rick C

Article: 159633
Subject: Anyone use 1's compliment or signed magnitude?
From: Tim Wescott <seemywebsite@myfooter.really>
Date: Tue, 24 Jan 2017 22:44:32 -0600
Links: << >>  << T >>  << A >>
This is kind of a survey; I need some perspective (possibly historical)

Are there any digital systems that you know of that use 1's compliment or 
signed-magnitude number representation for technical reasons?  

Have you ever used it in the past?

Is the world down to legacy applications and interfacing with legacy 
sensors?

TIA.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Article: 159634
Subject: Hardware floating point?
From: Tim Wescott <seemywebsite@myfooter.really>
Date: Tue, 24 Jan 2017 22:59:16 -0600
Links: << >>  << T >>  << A >>
So, just doing a brief search, it looks like Altera is touting a floating 
point slice in at least one of their lines.

Is this really a thing, or are they wrapping some more familiar fixed-
point processing with IP to make it floating point?

And, anything else you know.

TIA.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Article: 159635
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 01:23:44 -0500
Links: << >>  << T >>  << A >>
On 1/24/2017 11:44 PM, Tim Wescott wrote:
> This is kind of a survey; I need some perspective (possibly historical)
>
> Are there any digital systems that you know of that use 1's compliment or
> signed-magnitude number representation for technical reasons?
>
> Have you ever used it in the past?
>
> Is the world down to legacy applications and interfacing with legacy
> sensors?

Not sure I can be of a lot of help, but I do know these have been used 
in various systems in the past.  1's compliment has an advantage of not 
needing an adder to negate a number.  in 1's compliment the negative is 
just all bits inverted.  So some of the early computers used it for that 
reason.  Addition is slightly complicated, or I should say subtraction 
since you must add a one to make the result come out right.  Not a big 
deal as you can use the carry input to the lsb.  Then there is the issue 
of having two zeros, 000...0 and 111...1 are both zero.  lol

I have seen sign magnitude used in ADCs.  I believe in some designs it 
is simpler to produce a magnitude and then just append a sign bit rather 
than adding the logic to create a two's complement number.  In the old 
days the analog technology didn't lend itself to the logic so well. 
Otherwise I have not seen sign magnitude used anywhere or in any 
computers.

In some of the rather old business computers they used various forms of 
BCD or excess 3 code to simplify arithmetic since converting between 
binary and decimal digits can be a fair amount of work when you don't 
have fancy hardware.

-- 

Rick C

Article: 159636
Subject: Re: Hardware floating point?
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 01:58:07 -0500
Links: << >>  << T >>  << A >>
On 1/24/2017 11:59 PM, Tim Wescott wrote:
> So, just doing a brief search, it looks like Altera is touting a floating
> point slice in at least one of their lines.
>
> Is this really a thing, or are they wrapping some more familiar fixed-
> point processing with IP to make it floating point?
>
> And, anything else you know.

I'm not sure what you are asking.  What do you think floating point is 
exactly?  The core of floating point is just fixed point arithmetic with 
an extra bit (uh, rereading this I need to make clear this is the 
British "bit" meaning part :) to express the exponent of a binary 
multiplier.  To perform addition or subtraction on floating point 
numbers the mantissa needs to be normalized meaning the bits must be 
lined up so they are all equal weight.  This requires adjusting one of 
the exponents so the two are equal while shifting the mantissa to match. 
  Then the addition can be done on the mantissa and the result adjusted 
so the msb of the mantissa is in the correct alignment.

Multiplication is actually easier in that normalization is not required, 
but exponents are added and the result is adjusted for correct alignment 
of the mantissa.

So the heart of a floating point operation is a fixed point ALU with 
barrel shifters before and after.

-- 

Rick C

Article: 159637
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: cfbsoftware@gmail.com
Date: Wed, 25 Jan 2017 02:59:46 -0800 (PST)
Links: << >>  << T >>  << A >>
On Wednesday, January 25, 2017 at 3:14:39 PM UTC+10:30, Tim Wescott wrote:
> This is kind of a survey; I need some perspective (possibly historical)
>=20
> Are there any digital systems that you know of that use 1's compliment or=
=20
> signed-magnitude number representation for technical reasons? =20
>=20
> Have you ever used it in the past?
>=20

Quote:

"Some designers chose 1=E2=80=99s complement, where =E2=88=92n was obtained=
 from n by simply inverting all bits. Some chose 2=E2=80=99s complement, wh=
ere =E2=88=92n is obtained by
inverting all bits and then adding 1. The former has the drawback of featur=
ing two forms for zero (0=E2=80=A60 and 1=E2=80=A61). This is nasty, partic=
ularly if available comparison instructions are inadequate. For example, th=
e CDC 6000 computers had an instruction that tested for zero, recognizing b=
oth forms
correctly, but also an instruction that tested the sign bit only, classifyi=
ng 1=E2=80=A61 as a negative number, making comparisons unnecessarily compl=
icated. This case of inadequate design reveals 1=E2=80=99s complement as a =
bad idea. Today, all computers use 2=E2=80=99s complement arithmetic."

Ref: "Good Ideas, Through the Looking Glass" Niklaus Wirth, IEEE Computer. =
Issue No. 01 - January (2006 vol. 39).

https://www.computer.org/csdl/mags/co/2006/01/r1028-abs.html


Article: 159638
Subject: Re: VHDL Editors (esp. V3S)
From: Anssi Saari <as@sci.fi>
Date: Wed, 25 Jan 2017 14:14:27 +0200
Links: << >>  << T >>  << A >>
thomas.entner99@gmail.com writes:

> As X and A's integrated editors are more or less limited, I guess many
> people will looking for better alternatives.

I suppose. What I remember of colleagues not using Emacs were using
Ultraedit in Windows or Nedit in Linux.

Others have used something with no language support (KWrite in Linux,
Sun's Textedit, also Windows Notepad, even "Edit" in MS-DOS.)

Article: 159639
Subject: Re: VHDL Editors (esp. V3S)
From: thomas.entner99@gmail.com
Date: Wed, 25 Jan 2017 06:25:12 -0800 (PST)
Links: << >>  << T >>  << A >>
> I suppose. What I remember of colleagues not using Emacs were using
> Ultraedit in Windows or Nedit in Linux.


But I think they do not go much beyond syntax highlighting for VHDL. Sigasi and V3S go much further, e.g. with automatic instance generation and "live" error checking.

@Tim: Do you have any specific Eclipse plug-ins in mind? I think they are all also just syntax highlighting. (For Verilog there is VEditor, but I think it has only limited VHDL support, too.) But it is some time ago since I checked last.

Article: 159640
Subject: Re: VHDL Editors (esp. V3S)
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 10:12:42 -0500
Links: << >>  << T >>  << A >>
On 1/25/2017 7:14 AM, Anssi Saari wrote:
> thomas.entner99@gmail.com writes:
>
>> As X and A's integrated editors are more or less limited, I guess many
>> people will looking for better alternatives.
>
> I suppose. What I remember of colleagues not using Emacs were using
> Ultraedit in Windows or Nedit in Linux.
>
> Others have used something with no language support (KWrite in Linux,
> Sun's Textedit, also Windows Notepad, even "Edit" in MS-DOS.)

I'm afraid I still use Codewright, which is a great tool still.  But 
it's not under Linux.  If I ever get a Linux computer up and running I 
keep saying I will switch to EMACS.  But when I've looked at it under 
Windows it seems crude and complicated.  I'm told once you get up the 
learning curve it is great, or grate.. pick one.

In Codewright I have several string recognizers to allow me to generate 
any one from any other, entity declaration, component instantiation, 
signals declarations.  Not so much pain until I start altering them.

-- 

Rick C

Article: 159641
Subject: Re: VHDL Editors (esp. V3S)
From: kkoorndyk <kris.koorndyk@gmail.com>
Date: Wed, 25 Jan 2017 07:32:55 -0800 (PST)
Links: << >>  << T >>  << A >>
On Saturday, January 21, 2017 at 7:36:46 PM UTC-5, thomas....@gmail.com wro=
te:
> As X and A's integrated editors are more or less limited, I guess many pe=
ople will looking for better alternatives.
>=20
> The usual suspects will be Emacs (with VHDL mode) and Sigasi.
>=20
> For me personally, I never really liked Emacs and found Sigasi just a bit=
 too expensive.
>=20
> So some time ago I came across V3S from www.vide-software.at. It is a qui=
te powerful and fair priced VHDL plug-in for Visual Studio (Stand-alone ver=
sion with Visual Studio redistributable package also available). I could al=
so watch the progress over the last few months and I really like it.
>=20
> The only drawback is the missing Linux support. However, there appears to=
 be a Linux version of "Visual Studio Code". I have not checked yet if this=
 works together with the plug-in. Maybe someone else has?
>=20
> Regards,
>=20
> Thomas
>=20
> P.S.: I am in no way related to V3S, just a happy user. I want to sell yo=
u EEBlasters, JPEG encoders and cameras at www.entner-electronics.com, howe=
ver ;-)

As far as "editors" go, take your pick.  I've used Emacs almost exclusively=
 for ~15 years.  Once you're proficient with something, it's difficult to s=
witch.  I use it on Windows and Linux with no problems.  It does take a whi=
le to set it up the way you like it, but once you learn the commands it's r=
eally nice.

Other editors used by my colleagues (some that I've tried) include: Vim, gV=
im, neoVim, Atom, Sublime Text, Notepad++, and SlickEdit.

One of the features I use a lot is Rectangle mode in Emacs.  https://www.em=
acswiki.org/emacs/RectangleCommands

I haven't found a good, easy way to do the same thing in any of the other e=
ditors and that alone is a primary reason for sticking with Emacs.

Article: 159642
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: GaborSzakacs <gabor@alacron.com>
Date: Wed, 25 Jan 2017 10:46:16 -0500
Links: << >>  << T >>  << A >>
Tim Wescott wrote:
> This is kind of a survey; I need some perspective (possibly historical)
> 
> Are there any digital systems that you know of that use 1's compliment or 
> signed-magnitude number representation for technical reasons?  
> 
> Have you ever used it in the past?
> 
> Is the world down to legacy applications and interfacing with legacy 
> sensors?
> 
> TIA.
> 

If by "signed-magnitude" you mean "sign-magnitude", i.e. numbers are
always positive binary encoding with a separate sign bit, then most
floating point formats use it for the mantissa.  Once again you have
the possibility of positive and negative zero, however IEEE floating
formats don't allow negative zero in the standard encoding, so you need
to check for zero when negating a number.  Zero is a special case in
these formats, because otherwise there is an assumed 1 to the left of
the mantissa.  The same formats use offset binary for the exponent.

-- 
Gabor

Article: 159643
Subject: Re: VHDL Editors (esp. V3S)
From: Rob Gaddi <rgaddi@highlandtechnology.invalid>
Date: Wed, 25 Jan 2017 08:46:28 -0800
Links: << >>  << T >>  << A >>
On 01/25/2017 07:32 AM, kkoorndyk wrote:
> On Saturday, January 21, 2017 at 7:36:46 PM UTC-5, thomas....@gmail.com wrote:
>> As X and A's integrated editors are more or less limited, I guess many people will looking for better alternatives.
>>
>> The usual suspects will be Emacs (with VHDL mode) and Sigasi.
>>
>> For me personally, I never really liked Emacs and found Sigasi just a bit too expensive.
>>
>> So some time ago I came across V3S from www.vide-software.at. It is a quite powerful and fair priced VHDL plug-in for Visual Studio (Stand-alone version with Visual Studio redistributable package also available). I could also watch the progress over the last few months and I really like it.
>>
>> The only drawback is the missing Linux support. However, there appears to be a Linux version of "Visual Studio Code". I have not checked yet if this works together with the plug-in. Maybe someone else has?
>>
>> Regards,
>>
>> Thomas
>>
>> P.S.: I am in no way related to V3S, just a happy user. I want to sell you EEBlasters, JPEG encoders and cameras at www.entner-electronics.com, however ;-)
>
> As far as "editors" go, take your pick.  I've used Emacs almost exclusively for ~15 years.  Once you're proficient with something, it's difficult to switch.  I use it on Windows and Linux with no problems.  It does take a while to set it up the way you like it, but once you learn the commands it's really nice.
>
> Other editors used by my colleagues (some that I've tried) include: Vim, gVim, neoVim, Atom, Sublime Text, Notepad++, and SlickEdit.
>
> One of the features I use a lot is Rectangle mode in Emacs.  https://www.emacswiki.org/emacs/RectangleCommands
>
> I haven't found a good, easy way to do the same thing in any of the other editors and that alone is a primary reason for sticking with Emacs.
>

I know that Notepad++ (Windows) and Geany (my personal choice, 
cross-platform) both support column selection, which I think is pretty 
equivalent to Rectangle mode for most code sorts of tasks.  They're both 
based around Scintilla as a backend; I'm assuming the support goes all 
the way back to that.

-- 
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order.  See above to fix.

Article: 159644
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: Jon Elson <jmelson@wustl.edu>
Date: Wed, 25 Jan 2017 13:42:45 -0600
Links: << >>  << T >>  << A >>
Tim Wescott wrote:

> This is kind of a survey; I need some perspective (possibly historical)
> 
> Are there any digital systems that you know of that use 1's compliment or
> signed-magnitude number representation for technical reasons?
> 
The LINC computer used 1's complement.  Having two zeros that did not 
compare as equal was a pain!

Jon

Article: 159645
Subject: Re: Hardware floating point?
From: Kevin Neilson <kevin.neilson@xilinx.com>
Date: Wed, 25 Jan 2017 14:07:02 -0800 (PST)
Links: << >>  << T >>  << A >>
> I'm not sure what you are asking.  What do you think floating point is 
> exactly?  The core of floating point is just fixed point arithmetic with 
> an extra bit (uh, rereading this I need to make clear this is the 
> British "bit" meaning part :) to express the exponent of a binary 
> multiplier.  To perform addition or subtraction on floating point 
> numbers the mantissa needs to be normalized meaning the bits must be 
> lined up so they are all equal weight.  This requires adjusting one of 
> the exponents so the two are equal while shifting the mantissa to match. 
>   Then the addition can be done on the mantissa and the result adjusted 
> so the msb of the mantissa is in the correct alignment.
> 
> Multiplication is actually easier in that normalization is not required, 
> but exponents are added and the result is adjusted for correct alignment 
> of the mantissa.
> 

> So the heart of a floating point operation is a fixed point ALU with 
> barrel shifters before and after.

I think you oversimplify FP.  It works a lot better with dedicated hardware.  

Article: 159646
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: Tim Wescott <seemywebsite@myfooter.really>
Date: Wed, 25 Jan 2017 19:14:51 -0600
Links: << >>  << T >>  << A >>
On Wed, 25 Jan 2017 02:59:46 -0800, cfbsoftware wrote:

> On Wednesday, January 25, 2017 at 3:14:39 PM UTC+10:30, Tim Wescott
> wrote:
>> This is kind of a survey; I need some perspective (possibly historical)
>> 
>> Are there any digital systems that you know of that use 1's compliment
>> or signed-magnitude number representation for technical reasons?
>> 
>> Have you ever used it in the past?
>> 
>> 
> Quote:
> 
> "Some designers chose 1’s complement, where −n was obtained from n by
> simply inverting all bits. Some chose 2’s complement, where −n is
> obtained by inverting all bits and then adding 1. The former has the
> drawback of featuring two forms for zero (0…0 and 1…1). This is nasty,
> particularly if available comparison instructions are inadequate. For
> example, the CDC 6000 computers had an instruction that tested for zero,
> recognizing both forms correctly, but also an instruction that tested
> the sign bit only, classifying 1…1 as a negative number, making
> comparisons unnecessarily complicated. This case of inadequate design
> reveals 1’s complement as a bad idea. Today, all computers use 2’s
> complement arithmetic."
> 
> Ref: "Good Ideas, Through the Looking Glass" Niklaus Wirth, IEEE
> Computer. Issue No. 01 - January (2006 vol. 39).
> 
> https://www.computer.org/csdl/mags/co/2006/01/r1028-abs.html

I'm looking for current practice, not history.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Article: 159647
Subject: Re: Anyone use 1's compliment or signed magnitude?
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 20:25:06 -0500
Links: << >>  << T >>  << A >>
On 1/25/2017 8:14 PM, Tim Wescott wrote:
> On Wed, 25 Jan 2017 02:59:46 -0800, cfbsoftware wrote:
>
>> On Wednesday, January 25, 2017 at 3:14:39 PM UTC+10:30, Tim Wescott
>> wrote:
>>> This is kind of a survey; I need some perspective (possibly historical)
>>>
>>> Are there any digital systems that you know of that use 1's compliment
>>> or signed-magnitude number representation for technical reasons?
>>>
>>> Have you ever used it in the past?
>>>
>>>
>> Quote:
>>
>> "Some designers chose 1’s complement, where −n was obtained from n by
>> simply inverting all bits. Some chose 2’s complement, where −n is
>> obtained by inverting all bits and then adding 1. The former has the
>> drawback of featuring two forms for zero (0…0 and 1…1). This is nasty,
>> particularly if available comparison instructions are inadequate. For
>> example, the CDC 6000 computers had an instruction that tested for zero,
>> recognizing both forms correctly, but also an instruction that tested
>> the sign bit only, classifying 1…1 as a negative number, making
>> comparisons unnecessarily complicated. This case of inadequate design
>> reveals 1’s complement as a bad idea. Today, all computers use 2’s
>> complement arithmetic."
>>
>> Ref: "Good Ideas, Through the Looking Glass" Niklaus Wirth, IEEE
>> Computer. Issue No. 01 - January (2006 vol. 39).
>>
>> https://www.computer.org/csdl/mags/co/2006/01/r1028-abs.html
>
> I'm looking for current practice, not history.

Other than the few ADC parts I described that use sign-magnitude, I'm 
pretty sure you won't find any computers using either 1's complement or 
sign-magnitude.  Pocket calculators likely still use BCD.  Otherwise 
everything is 2's complement binary.

-- 

Rick C

Article: 159648
Subject: Re: Hardware floating point?
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 20:39:54 -0500
Links: << >>  << T >>  << A >>
On 1/25/2017 5:07 PM, Kevin Neilson wrote:
>> I'm not sure what you are asking.  What do you think floating point is
>> exactly?  The core of floating point is just fixed point arithmetic with
>> an extra bit (uh, rereading this I need to make clear this is the
>> British "bit" meaning part :) to express the exponent of a binary
>> multiplier.  To perform addition or subtraction on floating point
>> numbers the mantissa needs to be normalized meaning the bits must be
>> lined up so they are all equal weight.  This requires adjusting one of
>> the exponents so the two are equal while shifting the mantissa to match.
>>   Then the addition can be done on the mantissa and the result adjusted
>> so the msb of the mantissa is in the correct alignment.
>>
>> Multiplication is actually easier in that normalization is not required,
>> but exponents are added and the result is adjusted for correct alignment
>> of the mantissa.
>>
>
>> So the heart of a floating point operation is a fixed point ALU with
>> barrel shifters before and after.
>
> I think you oversimplify FP.  It works a lot better with dedicated hardware.

Not sure what your point is.  The principles are the same in software or 
hardware.  I was describing hardware I have worked on.  ST-100 from Star 
Technologies.  I became very intimate with the inner workings.

The only complications are from the various error and special case 
handling of the IEEE-754 format.  I doubt the FPGA is implementing that, 
but possibly.  The basics are still the same.  Adds use a barrel shifter 
to denormalize the mantissa so the exponents are equal, a integer adder 
and a normalization barrel shifter to produce the result.  Multiplies 
use a multiplier for the mantissas and an adder for the exponents (with 
adjustment for exponent bias) followed by a simple shifter to normalize 
the result.

Both add and multiply are about the same level of complexity as a barrel 
shifter is almost as much logic as the multiplier.

Other than the special case handling of IEEE-754, what do you think I am 
missing?

-- 

Rick C

Article: 159649
Subject: Re: VHDL Editors (esp. V3S)
From: rickman <gnuarm@gmail.com>
Date: Wed, 25 Jan 2017 20:46:37 -0500
Links: << >>  << T >>  << A >>
On 1/25/2017 10:32 AM, kkoorndyk wrote:
> On Saturday, January 21, 2017 at 7:36:46 PM UTC-5, thomas....@gmail.com wrote:
>> As X and A's integrated editors are more or less limited, I guess many people will looking for better alternatives.
>>
>> The usual suspects will be Emacs (with VHDL mode) and Sigasi.
>>
>> For me personally, I never really liked Emacs and found Sigasi just a bit too expensive.
>>
>> So some time ago I came across V3S from www.vide-software.at. It is a quite powerful and fair priced VHDL plug-in for Visual Studio (Stand-alone version with Visual Studio redistributable package also available). I could also watch the progress over the last few months and I really like it.
>>
>> The only drawback is the missing Linux support. However, there appears to be a Linux version of "Visual Studio Code". I have not checked yet if this works together with the plug-in. Maybe someone else has?
>>
>> Regards,
>>
>> Thomas
>>
>> P.S.: I am in no way related to V3S, just a happy user. I want to sell you EEBlasters, JPEG encoders and cameras at www.entner-electronics.com, however ;-)
>
> As far as "editors" go, take your pick.  I've used Emacs almost exclusively for ~15 years.  Once you're proficient with something, it's difficult to switch.  I use it on Windows and Linux with no problems.  It does take a while to set it up the way you like it, but once you learn the commands it's really nice.
>
> Other editors used by my colleagues (some that I've tried) include: Vim, gVim, neoVim, Atom, Sublime Text, Notepad++, and SlickEdit.
>
> One of the features I use a lot is Rectangle mode in Emacs.  https://www.emacswiki.org/emacs/RectangleCommands
>
> I haven't found a good, easy way to do the same thing in any of the other editors and that alone is a primary reason for sticking with Emacs.

The description of rectangle mode is a bit complex, how do you get an 
odd number of characters with an even number of lines?  But Codewright 
has what I think that mode does.  They call it block mode and you can 
cut, copy and paste any rectangular region to anywhere else.

I just realized that one of the "oddities" of Codewright has to do with 
the way they handle the blank spaces with no characters.  If you 
position the cursor on a line where no chars are typed and type 
anything, it inserts spaces (or tabs and spaces) ahead of the cursor 
from the last char on the line.  This would be important when using 
block mode in many instances.  It's a bit of a pain in that moving the 
cursor down does not position at the end of the line, rather it just 
moves down one.  You have to press the "end" key to go to the end of the 
line even when it is to the left.  :(

-- 

Rick C



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