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Messages from 96825

Article: 96825
Subject: Re: Async Processors
From: Allan Herriman <allanherriman@hotmail.com>
Date: Sat, 11 Feb 2006 14:12:43 +1100
Links: << >>  << T >>  << A >>
On 10 Feb 2006 13:40:44 -0800, fpga_toys@yahoo.com wrote:

>
>Andy Peters wrote:
>> fpga_toys@yahoo.com wrote:
>> > rickman wrote:
>> > > If your VOIP started dropping packets so that your phone calls were
>> > > garbled and the provider said, "of course, we had a hot day, do you
>> > > expect to see the same speeds all the time?", would you find that
>> > > acceptable?
>> >
>> > IT HAPPENS!!!  Reality Check ... IT HAPPENS EVERY DAY.
>>
>> Packets are dropped, but for congestion reasons, not because the air
>> handling in the switch room set the temperature up a few degrees.
>
>It happens when the router is unable to keep up with the traffic, aka
>congestion.
>Doesn't really matter why it's slower than the arrival rate.
>
>If async can deliver a faster packet processing rate when the
>environmentals
>are better, then the cogestion point is moved higher for those periods,
>unlike
>being locked to worst case performance.

Have you ever designed a router?

Most packets are handled by the data plane.  Packets will be dropped
if there's congestion even if the logic is infinitely fast, so any
argument about async or sync is moot.  (However these would typically
be designed with sync logic for sound engineering reasons.)

A (hopefully small) subset of packets are handled by the control
plane, and throughput and latency are improved by having a faster
processor.  It doesn't matter whether its internal processing is async
or sync, as long as it is as fast as possible and it can interface to
the various sync devices surrounding it (memories, backplane, etc.).

Regards,
Allan

Article: 96826
Subject: Re: Async Processors
From: fpga_toys@yahoo.com
Date: 10 Feb 2006 20:00:36 -0800
Links: << >>  << T >>  << A >>

Allan Herriman wrote:
> Have you ever designed a router?

yes, and no. I've built routers out of comodity parts, but not an ASIC
or FPGA one.

> Most packets are handled by the data plane.  Packets will be dropped
> if there's congestion even if the logic is infinitely fast, so any
> argument about async or sync is moot.  (However these would typically
> be designed with sync logic for sound engineering reasons.)

Only on current production high end routers. Consumer routers still
seem to be processor based, as a good sided FPGA/ASIC for a router core
still seems to be out of reach for a $49 wireless retail router or
wireless router.

> A (hopefully small) subset of packets are handled by the control
> plane, and throughput and latency are improved by having a faster
> processor.  It doesn't matter whether its internal processing is async
> or sync, as long as it is as fast as possible and it can interface to
> the various sync devices surrounding it (memories, backplane, etc.).


Certainly true on larger wire speed routers.  But again, only on the
high end gear at this point.


Article: 96827
Subject: Re: FPGA-Programmable power supply
From: "wicky" <wicky.zhang@gmail.com>
Date: 10 Feb 2006 22:30:29 -0800
Links: << >>  << T >>  << A >>

panteltje@yahoo.com wrote:
> Alex Gibson wrote:
>
> > > You do not need an fpga for this but
> > >
> > > With PWM , simple closed loop control and a LC filter can solve your
> > > problem.
> > > A FPGA adds 7 segment display, a few buttons to adjust voltage manually
> > > or
> > > even RS-232 control is very feasable.
> > > ok you have a fpga then you can make it multiple output power supply.
> > >
> > > Just for fun add sinusoidal outputs to make it universal.(Again PWM)
> > >
> > > yusuf
> >
> > Could do the same with a pic or even a cpld
> Well, Sunday, and was just thinking about this a bit,
> In ANY case, when using FLASH based ROm or a FLASH based FPGA
> (and you will likely want a AD converter and these new  Actel FPGAs
> have
> one build in... then do the PWM.....
>  *  B U T  *
> We all know FLASH does not hold for ever,  I have some PSU that are 20
> years
> old and still work fine.
> So that begs the question WHAT will happen when a bit goes wrong in the
> EEPROM
> or FLASH FPGA?
> It *could* kick your programable FPGA output to max volts no curent
> limit !
> So I think that in case of a FLASH based micro controller, or FPGA (so
> not an analog
> solution, or ROM based ) one MUST provide a second circuit 'crowbar'
> and in this case
> 'programmable crowbar'.
>
> Then from that POV one should actually do the PWM and compare in
> analog, and only
> use the FPGA output to perhaps set some switches to select voltage
> range.
> You *can* specify 20 years max usage in your documentation, but if the
> thing
> blows up 1M$ lab equipment one day later I wonder if they could sue
> you.
>
> As for the OP .. his question implies zero knowledge of FPGA and likely
> electronics.
> So I referred to monkeys to explain it.
>
> Sunday .... it is going to be very cold here too this week......

Hi, you mean that flash memory isn't reliable, the same feeling to me.
:-)

But, when using flash-based fpga, you only need to read the
configuration data from flash memory and load them to configuration
sram once at the moment of power up. I think this would not a problem
even for such critical system. what do you think about it?

Best regards,

Wicky


Article: 96828
Subject: Creating low freq. clock on Altera FPGA
From: "avishay" <avishorp@yahoo.com>
Date: 11 Feb 2006 04:05:37 -0800
Links: << >>  << T >>  << A >>
Hello all,
I have to create a low speed clock (8KHz) out of a high speed one
(50MHz) on an Altera FPGA (Cyclone II). It has to be a real clock, not
a clock enable. PLL is of course out of question because this frequency
is out of its range. Trying to generate it with a simple couter
generates many warning, and in some cases Quartus reports that the
design does not meet time constraints. I tried to designate the
generated signal as a clock, but it doesn't improve the situation.
Is there another, "correct" way for doing this? Maybe I should insert
some kind of buffer after the counter? I would appreciate your advice.

Thanks,
Avishay Orpaz


Article: 96829
Subject: LVDS
From: "maxascent" <maxascent@yahoo.co.uk>
Date: Sat, 11 Feb 2006 07:10:21 -0600
Links: << >>  << T >>  << A >>
I am routing a pcb with a fpga and adc which has LVDS outputs. I am trying
to match the length of the signals. Will I be ok to match them to within
1mm. The max length of any signal will be 33mm and the adc is clocked at
250MHz.

Thanks

Jon


Article: 96830
Subject: which one among the available FPGAs is best for a fresher?
From: "chaitu11311@gmail.com" <chaitu11311@gmail.com>
Date: 11 Feb 2006 05:34:05 -0800
Links: << >>  << T >>  << A >>
hi, i am new to this field and studying my under graduate course on
FPGAs. to perform experiments practically i am planning to buy one
chip. so please suggest me which one among the available FPGAs suit me
so that i get in touch with it and also suggest me any softwares
available to interface the same with my pc.
thanks in advance
waiting for responce,
bye
chaitu


Article: 96831
Subject: Re: which one among the available FPGAs is best for a fresher?
From: "John Adair" <removethisthenleavejea@replacewithcompanyname.co.uk>
Date: Sat, 11 Feb 2006 13:48:10 -0000
Links: << >>  << T >>  << A >>
Chaitu

The two biggest suppliers of FPGAs Xilinx and Altera both have free software 
for their lower end device families Spartan and Cyclone respectively. 
Spartan-3 and Cyclone2 are the latest. Between them they have something like 
80-90% of the FPGA market so good to have experience of for finding jobs 
after graduation.

If you are looking to add a chip to one of your own circuits then you will 
want to look for a package that is easy to mount on a board. None of the 
modern packages are an easy solder onto a circuit unless you have profession 
kit especially BGA packages. If you just want to buy a board to use a number 
of vendors including ourselves have low cost products for students. We even 
have student based pricing under our UAP scheme.

John Adair
Enterpoint Ltd. - Home of Raggedstone1. The Low Cost Spartan-3 Development 
Board.
http://www.enterpoint.co.uk


<chaitu11311@gmail.com> wrote in message 
news:1139664844.963424.156820@g47g2000cwa.googlegroups.com...
> hi, i am new to this field and studying my under graduate course on
> FPGAs. to perform experiments practically i am planning to buy one
> chip. so please suggest me which one among the available FPGAs suit me
> so that i get in touch with it and also suggest me any softwares
> available to interface the same with my pc.
> thanks in advance
> waiting for responce,
> bye
> chaitu
> 



Article: 96832
Subject: Re: Xilinx 1.5v HSTL-I for QDR-II. Anybody successful with it?
From: "John Adair" <removethisthenleavejea@replacewithcompanyname.co.uk>
Date: Sat, 11 Feb 2006 14:03:06 -0000
Links: << >>  << T >>  << A >>
Ray

If is of assistance our Broaddown2 product will allow playing at 1.5V on 
most banks. Needs some solder bridges made but it is built in. We can do it 
also in a crude fashon on Raggedstone1 on 4 banks. Broaddown4 and Hollybush1 
(both showing shortly) will also have some capability as well.

John Adair
Enterpoint Ltd. - Home of Broaddown2. The Ultimate Spartan-3 Development 
Board.
http://www.enterpoint.co.uk

"Ray Andraka" <ray@andraka.com> wrote in message 
news:kpaHf.45966$bF.17191@dukeread07...
> We are considering a change to the IO standard used for the QDR-II 
> interface (1.5V HSTL Class 1 instead of 1.8V HSTL Class 1 (1.8V)). Xilinx 
> has not created any demo boards that use the 1.5V interfaces, but they 
> claim that it should work fine.
>
> Have any of you completed a Xilinx design that uses the 1.5V interfaces 
> (for QDR-II) or know of a successful development? 



Article: 96833
Subject: using FPGA in control field
From: "wicky" <wicky.zhang@gmail.com>
Date: 11 Feb 2006 07:15:26 -0800
Links: << >>  << T >>  << A >>
Hi all,

I want to use FPGA in control field. I know that uC or DSP processor is
a preferable choice to control engineer in general. But in my opinion,
the HDL-based logic inside FPGA is more appropriate for those high
performance needed but simple function tasks just as the role of a
controller in control system, while the C language can realize
complicated application. i.e. In my  control system, the controller
will be based on HDL inside FPGA to get a extremely high performance
and high reliability, while the rest of the work, such as
communication, data processing and human-machine interface will be
based on C language to get a more flexible system.

Certainly, the C-based embedded system may be implemented inside FPGA
to form a SOC system  and may be based on an OS for more convinent.

Can anyone give me some advice and papers about this idea?  thans a
lot.

Best Regards,

Wicky


Article: 96834
Subject: Re: Xilinx 1.5v HSTL-I for QDR-II. Anybody successful with it?
From: "Roger" <enquiries@rwconcepts.co.uk>
Date: Sat, 11 Feb 2006 16:04:05 GMT
Links: << >>  << T >>  << A >>
Ray,

Yes, one of my designs has a QDR with 1.5V HSTL-1 interfacing - no problems.

Rog.

"Ray Andraka" <ray@andraka.com> wrote in message 
news:kpaHf.45966$bF.17191@dukeread07...
> We are considering a change to the IO standard used for the QDR-II 
> interface (1.5V HSTL Class 1 instead of 1.8V HSTL Class 1 (1.8V)). Xilinx 
> has not created any demo boards that use the 1.5V interfaces, but they 
> claim that it should work fine.
>
> Have any of you completed a Xilinx design that uses the 1.5V interfaces 
> (for QDR-II) or know of a successful development? 



Article: 96835
Subject: Re: Creating low freq. clock on Altera FPGA
From: "Peter Alfke" <alfke@sbcglobal.net>
Date: 11 Feb 2006 08:29:14 -0800
Links: << >>  << T >>  << A >>
You can build a 13-bit synchronous and programmable counter,at 50 MHz
clock, in any modern FPGA. No problem.
Peter Alfke, Xilinx.
avishay wrote:
> Hello all,
> I have to create a low speed clock (8KHz) out of a high speed one
> (50MHz) on an Altera FPGA (Cyclone II). It has to be a real clock, not
> a clock enable. PLL is of course out of question because this frequency
> is out of its range. Trying to generate it with a simple couter
> generates many warning, and in some cases Quartus reports that the
> design does not meet time constraints. I tried to designate the
> generated signal as a clock, but it doesn't improve the situation.
> Is there another, "correct" way for doing this? Maybe I should insert
> some kind of buffer after the counter? I would appreciate your advice.
> 
> Thanks,
> Avishay Orpaz


Article: 96836
Subject: Re: using FPGA in control field
From: Tim Wescott <tim@seemywebsite.com>
Date: Sat, 11 Feb 2006 08:34:08 -0800
Links: << >>  << T >>  << A >>
wicky wrote:

> Hi all,
> 
> I want to use FPGA in control field. I know that uC or DSP processor is
> a preferable choice to control engineer in general. But in my opinion,
> the HDL-based logic inside FPGA is more appropriate for those high
> performance needed but simple function tasks just as the role of a
> controller in control system, while the C language can realize
> complicated application. i.e. In my  control system, the controller
> will be based on HDL inside FPGA to get a extremely high performance
> and high reliability, while the rest of the work, such as
> communication, data processing and human-machine interface will be
> based on C language to get a more flexible system.
> 
> Certainly, the C-based embedded system may be implemented inside FPGA
> to form a SOC system  and may be based on an OS for more convinent.
> 
> Can anyone give me some advice and papers about this idea?  thans a
> lot.
> 
> Best Regards,
> 
> Wicky
> 
Look at the highest sampling rate that will make a difference given the 
limitations of your plant.  If it's 10kHz or lower then you can just 
code your loop in C, run it on one of the newer DSP chips, and not have 
to mess around with FPGAs at all.  If it's 50kHz or lower then with a 
slight bit of extra work one of the newer DSP chips can be used with a 
moderate amount of assembly code and a careful trimming of other 
functionality.  If it's 100-200kHz then one of the newer DSP chips can 
be used, but the level of work necessary may be greater than the level 
of work necessary for your FPGA.

It's the rare plant that needs a loop sampling rate greater than 5-10kHz.

Don't expect the control rule to be all that simple -- one of the 
advantages of implementing a controller on a processor is that you can 
wrap it with all sorts of nonlinear frills to take care of corner cases 
that in an analog system you'd just have to live with, or do everything 
in your power to avoid.

Think hard about the reliability of implementing your controller in an 
FPGA.  Why should 1000 lines of Verilog be more reliable than 200 lines 
of C?

Ask yourself why you are stuck on one particular technology for 
implementing your control rule.  Control rules are just math; you should 
pick the implementation technology that makes the most sense for the 
problem at hand, be it a processor, FPGA, vacuum tube or hemp ropes and 
spinning mahogany drums.

-- 

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

Posting from Google?  See http://cfaj.freeshell.org/google/

Article: 96837
Subject: Re: LVDS
From: Allan Herriman <allanherriman@hotmail.com>
Date: Sun, 12 Feb 2006 03:38:21 +1100
Links: << >>  << T >>  << A >>
On Sat, 11 Feb 2006 07:10:21 -0600, "maxascent"
<maxascent@yahoo.co.uk> wrote:

>I am routing a pcb with a fpga and adc which has LVDS outputs. I am trying
>to match the length of the signals. Will I be ok to match them to within
>1mm. The max length of any signal will be 33mm and the adc is clocked at
>250MHz.

Short answer: yes.

Long answer:

I'm not quite clear about whether you mean length matching between the
various bits coming out of the ADC, or length matching between the P
and N signals in an LVDS pair of a single bit.

1.  Assume that you are referring to the length match between the bits
within the bus.

Divide 1mm by the speed of light in epoxy to get the skew between the
signals.  My mental ALU says this works out to be about 5ps.  Note
that this is *skew*.  You still have to ensure adequate timing margin
for each signal in the bus.  In this sense, the skew reduces your
timing margin, however, if you have to worry about 5ps when your clock
has a 4ns period, you have much bigger problems on your hands.

2.  Assume you are referring to the length match between the P and N
signals in an LVDS pair of an individual bit.

Normally for data signals this would be treated as in case 1, however
an ADC is sensitive to noise, and a length mismatch may result in a
small amount of differential mode to common mode conversion.  You
might want to do some spice modelling here, however I don't expect
you'll have a problem.


Also bear in mind that 1mm is probably better than the length match
inside the BGA package.  (I'm referring to the tracks between the
solder balls and the die pads.)  If you get really keen, you can
determine these lengths, and adjust the the lengths of the traces on
your pcb to compensate.
I did this once for a couple of 16 bit 622MHz buses.  It was a PITA to
do, and probably didn't make much real difference (it might have
changed the eye width from 73 to 74% or something like that).  The PCB
guy decided to change to software programming after that project.
Since then, we've changed to Expedition PCB from Mentor, and the (new)
PCB guy here says length matching including offsets is really easy to
do.


Another caveat: the velocity factor of a trace differs depending on
the layer inside the PCB.  Outer layers propagate signals faster due
to the lower effective permittivity!  This can cause problems with
length matching if you are not careful.  A good PCB tool will allow
you to specify the velocity factor independently for each layer.

Regards,
Allan

Article: 96838
Subject: Re: LVDS
From: "dp" <dp@tgi-sci.com>
Date: 11 Feb 2006 08:39:19 -0800
Links: << >>  << T >>  << A >>
maxascent wrote:
> I am routing a pcb with a fpga and adc which has LVDS outputs. I am trying
> to match the length of the signals. Will I be ok to match them to within
> 1mm. The max length of any signal will be 33mm and the adc is clocked at
> 250MHz.

Yes,  the apr. 6 pS skew because of the 1mm should
be negligible. In fact, I would say you'd still be safe with
10 times as much skew (10 mm length matching).

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------


Article: 96839
Subject: Re: using FPGA in control field
From: "wicky" <wicky.zhang@gmail.com>
Date: 11 Feb 2006 09:14:27 -0800
Links: << >>  << T >>  << A >>
Thanks for your rapid reply.

In fact, just as you said, It's the rare plant that needs a HDL-based
controller now, most of them will implemented with a DSP controller and
works well.

For the reliability, I know that HDL will be more complicated than C
language, what i mean is that something in hardware must be stronger
than that in software theoretically. As for the problem of code writing
of HDL, I think that G-language (graphic language tools such as DSP
Builder or System Generator) will decrease the difficulty observably.
Of course, they may loss some efficiency, but for the extremely high
performance you get in HDL controller, this problem will be less
sensitive than that of C language.

Now, G-language toos aren't mature enough. They can only generate codes
from simulink for some simple algorithm such as PID, if you want to try
some advanced alogrithm toolbox in simulink, you must write HDL codes
in hand.

For the consideration of cost, I think a HDL-based PID controller in a
low-cost FPGA such as ep1c6 will get at least a 10 times performance
than that of C2000 serials DSP  controller of TI.

Best regards,

Wicky


Article: 96840
Subject: Re: cheap USB analyzer based on FPGA
From: "Jerome" <nospam@nospam.com>
Date: Sat, 11 Feb 2006 18:18:42 +0100
Links: << >>  << T >>  << A >>
I checked with a scope after having insterted  "spy pins" in the middle of a 
AF/AM cable
--> swing is indeed 0v - 3.6V ."spyied" device was a Webcam, used SW was 
ampcap.

My scope is old and unaccurate , i'm not sure of the exact acceptable level 
for NON 5V tolerant devices
(3.3V? 3.6V?...)

When using live video, there are data frame of length ~40 ms & period ~50 ms
When "zooming", i can see the USB full speed frames every 1 ms.
Theses frames have a duration of ~200 - 250 us when live video is enabled

When no video is enabled, the 1ms frame are still threre but no data


"mk" <kal*@dspia.*comdelete> wrote in message 
news:dgbju1hnj345uddqmf0g7ed58ss12gnaga@4ax.com...
> On Wed, 8 Feb 2006 07:18:46 +0100, "Jerome" <nospam@nospam.com> wrote:
>
>>Thanks Eric,
>>However concerning the 5V tolerance, i'm not sure it is necessary since 
>>the
>>D+ & D- level swing
>>stays in the 0V - 3.6 V range
>>
>>My first step will consist in measuring these levels with a scope
>
> Those levels are OK but in USB spec there is a tolerance to short to
> 5V requirement which is why it's mentioned. In a controlled
> environment you don't need 5V tolerance on the data inputs.
> 



Article: 96841
Subject: Re: Async Processors
From: Allan Herriman <allanherriman@hotmail.com>
Date: Sun, 12 Feb 2006 04:25:17 +1100
Links: << >>  << T >>  << A >>
On 10 Feb 2006 20:00:36 -0800, fpga_toys@yahoo.com wrote:

>
>Allan Herriman wrote:
>> Have you ever designed a router?
>
>yes, and no. I've built routers out of comodity parts, but not an ASIC
>or FPGA one.
>
>> Most packets are handled by the data plane.  Packets will be dropped
>> if there's congestion even if the logic is infinitely fast, so any
>> argument about async or sync is moot.  (However these would typically
>> be designed with sync logic for sound engineering reasons.)
>
>Only on current production high end routers. Consumer routers still
>seem to be processor based, as a good sided FPGA/ASIC for a router core
>still seems to be out of reach for a $49 wireless retail router or
>wireless router.
>
>> A (hopefully small) subset of packets are handled by the control
>> plane, and throughput and latency are improved by having a faster
>> processor.  It doesn't matter whether its internal processing is async
>> or sync, as long as it is as fast as possible and it can interface to
>> the various sync devices surrounding it (memories, backplane, etc.).
>
>
>Certainly true on larger wire speed routers.  But again, only on the
>high end gear at this point.

The end customers would describe your hypothetical low end box as a
router, but in the context of this discussion (and newsgroup), it's
just a general purpose processor with some comms interfaces with some
software that gives it some meaning.
In that context, I agree that a faster processor is a good thing, and
IF an async processor will give better performance (either in terms of
throughput, latency or power) on average, then it is also good.

Please bear in mind that most comms interfaces (e.g. Ethernet) are
synchronous in nature (at least at the physical layer).  One has real
time requirements to meet.
Synchronous design makes a lot of sense for a hardware router or
switch, etc.  (As it does for the products we design here, but I won't
bore you with the details.)

Regards,
Allan

Article: 96842
Subject: Re: cheap USB analyzer based on FPGA
From: Sylvain Munaut <com.246tNt@tnt>
Date: Sat, 11 Feb 2006 18:52:48 +0100
Links: << >>  << T >>  << A >>
How about using some resistors to reduce the swing, then use a
differential input of the FPGA ?


Jerome wrote:
> I checked with a scope after having insterted  "spy pins" in the middle of a 
> AF/AM cable
> --> swing is indeed 0v - 3.6V ."spyied" device was a Webcam, used SW was 
> ampcap.
> 
> My scope is old and unaccurate , i'm not sure of the exact acceptable level 
> for NON 5V tolerant devices
> (3.3V? 3.6V?...)
> 
> When using live video, there are data frame of length ~40 ms & period ~50 ms
> When "zooming", i can see the USB full speed frames every 1 ms.
> Theses frames have a duration of ~200 - 250 us when live video is enabled
> 
> When no video is enabled, the 1ms frame are still threre but no data
> 
> 
> "mk" <kal*@dspia.*comdelete> wrote in message 
> news:dgbju1hnj345uddqmf0g7ed58ss12gnaga@4ax.com...
> 
>>On Wed, 8 Feb 2006 07:18:46 +0100, "Jerome" <nospam@nospam.com> wrote:
>>
>>
>>>Thanks Eric,
>>>However concerning the 5V tolerance, i'm not sure it is necessary since 
>>>the
>>>D+ & D- level swing
>>>stays in the 0V - 3.6 V range
>>>
>>>My first step will consist in measuring these levels with a scope
>>
>>Those levels are OK but in USB spec there is a tolerance to short to
>>5V requirement which is why it's mentioned. In a controlled
>>environment you don't need 5V tolerance on the data inputs.

Article: 96843
Subject: Re: Xilinx 1.5v HSTL-I for QDR-II. Anybody successful with it?
From: Ray Andraka <ray@andraka.com>
Date: Sat, 11 Feb 2006 13:19:12 -0500
Links: << >>  << T >>  << A >>
Roger wrote:
> Ray,
> 
> Yes, one of my designs has a QDR with 1.5V HSTL-1 interfacing - no problems.
> 
> Rog.
> 
> "Ray Andraka" <ray@andraka.com> wrote in message 
> news:kpaHf.45966$bF.17191@dukeread07...
> 
>>We are considering a change to the IO standard used for the QDR-II 
>>interface (1.5V HSTL Class 1 instead of 1.8V HSTL Class 1 (1.8V)). Xilinx 
>>has not created any demo boards that use the 1.5V interfaces, but they 
>>claim that it should work fine.
>>
>>Have any of you completed a Xilinx design that uses the 1.5V interfaces 
>>(for QDR-II) or know of a successful development? 
> 
> 
> 

Thanks, that's what I needed to know.  A customer is making a custom 
board and wanted to know that the 1.5v HSTL worked before committing to it.

Article: 96844
Subject: Re: LVDS
From: "maxascent" <maxascent@yahoo.co.uk>
Date: Sat, 11 Feb 2006 14:01:09 -0600
Links: << >>  << T >>  << A >>
Thanks for everyones help, very usefull info.

Jon

Article: 96845
Subject: Re: Async Processors
From: fpga_toys@yahoo.com
Date: 11 Feb 2006 12:46:35 -0800
Links: << >>  << T >>  << A >>

rickman wrote:
> So the async design likely must have larger margins added to the design
> of the handshake path and the result is it will have a slower maximum
> speed compared to a sync design.

Simply not true for all async designs, especially those that generate
the ack function from the outputs of the local gates -- in those cases
there are no "margins" added at all, as it is implictly not necessary
by the design of the logic. This works well for fast routing and low
fanout, where gate delays are small and routing delays are small. For
larger designs, where the global clock skew rapidly exceeds these
timings, there is significant gain. 10 year old Phased Logic (ack
encoded as phase), and other async designs with ack based on logic
outputs (rather than a separate timing path) are a good example:

   http://www.erc.msstate.edu/mpl/projects/phased_logic

These designs compete well where global clock skew and environmental
margins greately exceed the typical timing of a logic element and short
route delay.


Article: 96846
Subject: Re: Async Processors
From: Jim Granville <no.spam@designtools.co.nz>
Date: Sun, 12 Feb 2006 11:22:00 +1300
Links: << >>  << T >>  << A >>
rickman wrote:

> Hey, if there is real data out there showing me how this works and that
> it is clearly better, fine.  I'm just saying this is not that sort of
> data.
> 
> 
<snip>
> 
> I'm not doubting the data, I'm doubting the comparison.  Do you see the
> difference?

( but above ) : "I'm just saying this is not that sort of data."

I'll leave others to decode that, I'm lost..

>>  Who claimed this was easy ? It's what they must have done
>>in the tools area, that impresses me as much as the
>>(claimed) silicon results.
> 
> 
> Yes, I am sure it was a lot of work and that is part of my concern with
> it.  But as long as it is *their* work, if they start making chips that
> solve my system problems better than other chips, then I'll use them.
> But this chip actually runs slower max speed in the same process.  Did
> you notice that?  The clocked processor runs up to 100 MHz, IIRC while
> the async processor was only 77 MHz room temp!

There is another, perhaps clearer press release here :

http://www.eet.com/news/design/showArticle.jhtml;jsessionid=RZAVAFCAIVCMGQSNDBECKHSCJUMEKJVN?articleID=179103395

Here, the key comparison is
"at equivalent performance the ARM996HS consumed a factor of 2.8 less 
power than the ARM968E-S, or 36 percent, according to simulation 
benchmark data from Handshake Solutions"

as I have said before, many designers will grab that with both hands.
If this is offered as FAB ready, those designers will not actually care 
about the details.

and they also say

"the ARM996HS is being promoted for its low electromagnetic footprint, 
another benefit of clockless performance which would make the processor 
core suitable for  automotive and mixed-signal applications."

Better EMC is also not to be sneezed at...

but I liked this comment too - Seemed very relevent...

" Richard York, ARMs ARM996HS product manager, said ARM would not rush 
to introduce clockless versions of other cores. It [asynchronous logic] 
will take some time to become widely accepted because it is very 
different, he told EE Times. " and
" A self-timed Cortex M3 would be a fascinating product but we want to 
see how this product goes in the market first. "

I look forward to the silicon, both ARM and 80C51 versions.

-jg





Article: 96847
Subject: Re: which one among the available FPGAs is best for a fresher?
From: fpga_toys@yahoo.com
Date: 11 Feb 2006 14:22:53 -0800
Links: << >>  << T >>  << A >>

John Adair wrote:
> If you are looking to add a chip to one of your own circuits then you will
> want to look for a package that is easy to mount on a board. None of the
> modern packages are an easy solder onto a circuit unless you have profession
> kit especially BGA packages. If you just want to buy a board to use a number
> of vendors including ourselves have low cost products for students. We even
> have student based pricing under our UAP scheme.

Actually, if looking to add an FPGA chip to one of your own designs,
BGA is by far the easiest for a hobbiest. Hand soldering a 100-200 pin
QFP varient package is a nightmare for a hobbiest without a stereo
microscope and a very fine low temp iron, and lots of aquired skill.
Even stenciling it is a nightmare, as it takes accurate placement to
avoid smearing the paste.

There are several tricks for prototype BGA assembly which work well for
a hobbiest, and a low volume commercial proto lab as well. Solder paste
for attachment is a super pain, as it requires accurate placement to
avoid smearing the paste - nearly impossible by hand without a
placement fixture. What works much better is to manually wet all the
BGA pads on the PCB by coating the PCB with ample water soluable flux
and dragging a large solder ball across all the pads with a fat
"screwdriver" soldering temp on a temp controlled iron -- do not
linger, to avoid heat damage to the pcb or device. Do this until all
the pads have a uniform solder bump and are shinny. This works equally
well for cleaning up a BGA device prior to reballing using the
SolderQuik preforms. Then wash off the expended flux, dry and bake to
remove any moisture trapped by the cleaning process to avoid popcorning
pads off.  Next, apply a liberal amount of water soluable flux to the
pcb and BGA balls, and carefully mate the balls to the pads by eye. If
you have a device outline on the pcb that is accurately registered to
the pads, this helps. (either copper, soldermask or silkscreen). It
sometimes help to bring two ball pads on the outside edge of the board
to a land large enough to touch with the soldering iron, which allows
fusing a ball on opposite sides/corners of the package to hold the
device in place during handling for assembly.  Ditto for QFP packages
-- prewetting the pads and leads with an iron, and then just fluxing
for assembly is sometimes easier than accurate placement with paste -
as you can always drag the iron with a little dangling solder across
the leads that didn't quite wet/attach with a fillet well enough.

If you have a toaster oven, take some time to calibrate it, and get a
temp stick.

     http://www.pcbexpress.com/stencils/stencil_article_page1.htm

Stencils for all the small parts which can be easily hand placed is a
great idea too.

While I use a couple Chipmaster SMD-1000's in my lab, I've also use my
wifes table top convection oven and a toaster oven for demonstrations
for local hobbiests. I suggest preheating the oven/toaster to about
325F and setting the project board into the preheated oven, then cycle
the oven/toaster up above soldering temp by 15-25 degrees and leave it
there about 2-3 times longer than the traditional temp profile of a
commercial reflow oven as there isn't quite as much energy available to
heat the board and parts to temp as quickly. This is where a temp stick
is useful, but not required.

It will generally take a few boards before you find exactly the perfect
process that leaves all the parts properly wetted and attached with
minimum heat and process time. For BGA's this is easy to confirm, by
making sure the balls all have a uniform "squat" which confirms the
inside balls came to temp, and wetted, allowing the package to fall
slightly and left the balls slightly compressed in shape.  All other
parts take a good magnifying glass or lab scope, and verify the wetting
left strong fillets on all the connections. Where the fillet is
obvious, but lacking in volume, take note as that pad needs a larger
paste mask opening next time.

Reballing BGA packages can be done the same way. But another process is
sometimes easier. That is to use a digital hot plate, or heavy electric
skillet and an inexpensive non-contact IR thermometer. Set the BGA in
the reballing frame on the preheated surface which is just over
soldering temp, and cover with a shinny preheated lid, and turn the
heat source off. The mass in the hot plate or skillet will bring the
BGA balls to temp, then cool back below plastic state. After a few
minutes remove the lid partially (lift one edge) to allow the device to
cool, but not hard shock it with cold air. Then remove and place on a
warm surface to further cool.


Article: 96848
Subject: Simulation problem using CONV_INTEGER
From: "Giox" <giovanniparodi79@yahoo.it>
Date: 11 Feb 2006 14:25:11 -0800
Links: << >>  << T >>  << A >>
I have the following code:

   signal busy_condition : std_logic;
   signal high_registered : std_logic_vector(1 downto 0);
   signal high_current : std_logic_vector(1 downto 0);


busy_condition <= '1'  WHEN	(CONV_INTEGER(high_current) >
CONV_INTEGER(high_registered))
	                 ELSE	'0';

During simulation
high_registered become "10"
and
high_current = "00".
However busy_condition is high impedence.
Is there someone that can explain me what is my error?
Thanks a lo Gio


Article: 96849
Subject: Re: using FPGA in control field
From: fpga_toys@yahoo.com
Date: 11 Feb 2006 15:06:52 -0800
Links: << >>  << T >>  << A >>

wicky wrote:
> For the reliability, I know that HDL will be more complicated than C
> language, what i mean is that something in hardware must be stronger
> than that in software theoretically. As for the problem of code writing
> of HDL, I think that G-language (graphic language tools such as DSP
> Builder or System Generator) will decrease the difficulty observably.
> Of course, they may loss some efficiency, but for the extremely high
> performance you get in HDL controller, this problem will be less
> sensitive than that of C language.


With good sized FPGA's falling in price, especially those with
processor cores or big enough for a soft processor core, it's actually
not that bad a design decision, and should just get better with time.

Consider Celoxica (Handel-C), Impulse (Streams-C) or even FpgaC as both
an HDL and an HLL for a lot of projects which might migrate from
microprocessors/DSP to FPGA.




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