Breaking News
Comments
Oldest First | Newest First | Threaded View
<<   <   Page 3 / 3
DrFPGA
User Rank
Blogger
Re: math links
DrFPGA   12/9/2013 11:02:27 AM
NO RATINGS
Remember when we had to do many of the FPGA tricks by hand? Register retiming, one hot state machines, if then else to mux conversions? Now the synthesis tools do all this for us. Hopefully tricks like the multiply by a constant will get folded in too. Just depends on how common the need is for these tricks I guess.

Maybe there should be a 'list' of tricks that users suggest would be good to put into synthesis tools. Perhaps via a discussion thread on Programmable Logic Design Line?

betajet
User Rank
CEO
Know the limitations of your tools
betajet   12/9/2013 2:20:02 PM
NO RATINGS
I remember the first time I synthesized an FPGA design for a real product.  The synthesizer automatically came up with a one-hot state machine coding.  Everything simulated fine.   Unfortunately, this particular design did not have a well-formed clock when connecting or disconnecting the input signal, which would cause it to lose the one-hot code occasionally when reconnecting.  Switching to a manual state coding that automatically recovered from bad states fixed the problem -- and saved logic cells in this case.

Lesson 1:  Don't trust automatic state assignment.  Some synthesizers make it hard to turn off automatic state assignment, but it's worth the effort.

Lesson 2:  Don't trust simulation.  It only simulates theoretical models, not the real world.

Lessons 1+2 combined and generalized:  Know the limitations of your tools.

DrFPGA
User Rank
Blogger
Re: Know the limitations of your tools
DrFPGA   12/9/2013 2:37:47 PM
NO RATINGS
Very important point and one difficult to do in practice. How many tools actually document (in detail) what the tool will do or not do. I find I need to do small example designs and look over th output of the place and route tool to figure out what is going on. Widh the vendors did this for me!

Anyone else have tools with detailed enough docs that they can tell ahead of time what is being done?

paragdighe
User Rank
Rookie
its fixed point math
paragdighe   12/10/2013 4:45:31 AM
NO RATINGS
1 saves
here's why it works: x/10=x*0.1={2^16*x*0.1}/2^16={x*2^16*0.1}/2^16 =x*1999H/2^16 

<<   <   Page 3 / 3


Flash Poll
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Rishabh N. Mahajani, High School Senior and Future Engineer

Future Engineers: Don’t 'Trip Up' on Your College Road Trip
Rishabh N. Mahajani, High School Senior and Future Engineer
3 comments
A future engineer shares his impressions of a recent tour of top schools and offers advice on making the most of the time-honored tradition of the college road trip.

Max Maxfield

Juggling a Cornucopia of Projects
Max Maxfield
19 comments
I feel like I'm juggling a lot of hobby projects at the moment. The problem is that I can't juggle. Actually, that's not strictly true -- I can juggle ten fine china dinner plates, but ...

Larry Desjardin

Engineers Should Study Finance: 5 Reasons Why
Larry Desjardin
38 comments
I'm a big proponent of engineers learning financial basics. Why? Because engineers are making decisions all the time, in multiple ways. Having a good financial understanding guides these ...

Karen Field

July Cartoon Caption Contest: Let's Talk Some Trash
Karen Field
144 comments
Steve Jobs allegedly got his start by dumpster diving with the Computer Club at Homestead High in the early 1970s.

Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)