8 Replies Latest reply on Jan 27, 2012 11:09 PM by sabitha.jamal

    Design entry, does it meet your needs?


      At this time, schematic CAD packages have existed for more than 30 years.  Many packages have been bought out and merged into other systems, some have taken on life in small specialized roles, and others have tried to be all things to all users.


      My background is in PCB and Spice packages, and a lot of different features have been in many packages. One package for spice features layers that can be turned on and off so that different blocks could be simulated in different ways without changing the base circuit.  A component on one layer may or may not be on other layers.  A second package lets the designer draw a net over and through components and it automatically connects every vertex that is not blocked by a component and for those that are blocked will create a new net for very quick connections.  Several schematic packages now allow spreadsheet type inputs with no graphical requirement at all.



      I would be interested in your thoughts on how to improve and develop better design entry methods.


      * Are today's Schematic packages meeting your needs?
      * Is the output easy to share?


      • What types of outputs are required?

      • Does your design entry need to power several different tools such as both PCB and simulation?


        • 1. Re: Design entry, does it meet your needs?


          One of the items you mentioned below was spreadsheet based entry. While the new ICE Tables available in DxD2007 do allow quick and easy connectivity, the documentation of these types of design elements is still somewhat of a challenge. How do you see the most effective way to ensure this infomation can be presented in a usable fashion for debugging & design review?






          • 2. Re: Design entry, does it meet your needs?


            I see the spreadsheet editor most useful for large Busses with nets going from one part to other components.  For example, memory bus routing.  The nets have similar rules, most are pin to pin, with resistor termination.



            • 3. Re: Design entry, does it meet your needs?


              OK - so for large buses (let's start w/ a hypothetical bus of 32 bits) that connect 2 ICs with in-line termination, what would be the most effective way the debug team should use the ICE Tables from a documentation standpoint?  This type of table would show a 32-bit bus on the left hand side & the block definition & 34 components (the 2 ICs & 32 resistors) across the top.






              Understanding how to articulate solutions to this type of situation will be very useful in driving adoption and acceptance in the user community.



              • 4. Re: Design entry, does it meet your needs?



                  VHDL was started by the DoD as a standard Documentation language!  From an engineering perspective I like VHDL and Verilog but I have never thought of them as "documentation".  I am a visual processor. Block Diagrams, schematics have always been the easiest method I have found to share "design intent" and provide "documentation".


                  However, as devices have grown in pin count (1500 pin FPGA BGA for example) we {the engineering fraternity} have developed all sorts of creative methods to use our "tried and true" schematic capture process such as creating multiple Fractured symbols for a single large device.  When you have 10 fractured symbols, each with 150 pins the clear representation of the "schematic visual flow" is lost.


                  I adopted hierarchical schematic design as the most logical method for dealing with complexity:


                • The top level is a block diagram that maintains the logical "visual" flow of the design

                • Within each block I would use either more hierarchy to decompose the logic visually or I would get into the detailed design using any number of techniques (the fractured symbols, HDLs - for the FPGA, etc..)


                From my perspective the ICT tables aren't any different than HDL in the sense that they provide an accelerated form of design entry while loosing the visual projection of design intent.


                  I would argue that as design complexity has increased schematic entry has in effect stymied productivity and the nature of the complexity, even with a schematic, has lost the ability to serve as a visual "design intent" documentation. It is the mix of design entry techniques that preserves design intent while promoting design productivity. I think there is a good reason why chip design rapidly progressed from schematic design to HDL design and it is more than the advent of synthesis technologies. The simple fact is and was that design complexity increased to the point where although you could create a schematic the ability to follow the logic was limited by the immense size of the design.  I think we are at the same point with PCB designs that use large BGA packages.


                  The strange twist that I have encountered is that many PCB designers avoid hierarchy preferring large multi-sheet flat designs. Using this technique I do not know how anyone is able to follow the design intent on complex designs. It is my recommendation to use the top level of the design as a functional block to visually represent design intent and then decompose the design through whatever design entry method promotes productivity to complete the detailed design description.


                  I'm an old dog.  When I first started we created our designs by typing in netlists.  I was obviously very attracted to schematic entry as a productivity enabler as the only way I could create the netlist was to sketch the design on paper and then enter the netlist.  The schematic entry process resolved this dual entry (error prone) process.


                Managing complexity while promoting productivity is where I think ICT table fit in.  You are correct, it is more than the technology of design entry we need structured processes to complete the entire task of design entry plus design documentation.

                • 5. Re: Design entry, does it meet your needs?





                  Thank you for post.



                  A couple of things that  I see as I read your info that seperate the desciption of the functionality of a chip from the functionality of a board


                  • HDLs were primarily (not exclusively) aimed at functionality of an individual chip, which is not something a diagnostic engineer would touble shoot in the field like he would a board

                  • Also in the HDL world there are multiple approachs to generating graphical representations of portions of the design which articulate behavior (state diagrams, block diagrams, flow charts, etc) for debug purposes


                  I also agree whole heartily with your hierarchy approach.  I as well think in level not sheets.



                  What I would like to accomplish is to drive this same type of approach (or maybe even options) to feed diagnostic or field troubleshooting employees.  Even if it does not auto-gen the whole enchilada - maybe sub-sections would be a good start.






                  • 6. Re: Design entry, does it meet your needs?



                    You are spot on.


                      If we look at the definition of "VHDL", it  is properly decomposed to an acronym withing an acronym:


                    • VHSIC Hardware Description Language


                      • VHSIC == Very High Speed Integrated Circuit


                    I guess we are always working on Very High Speed designs 


                    For a few years I was the Product Marketing Manager for FPGA Advantage which included HDL Designer. One of the capabilities of HDL Designer was the ability to generate graphic representations of the HDL.  A very useful documentation and debugging tool.


                    Many years ago, I worked on a product called Schematic Generator which essentially took a structural netlist and created a schematic.  While I appreciated the functionality, working with customers I quickly learned that creating a schematic that provided clear visual flow was a task in either "art" or "futility". What was beautiful and meaningful to one engineer was noise and garbage to another.


                    I do take your point; generating a graphical representation from an ICT might provide both productivity and documentation. While I will not promise that we will implement anything, I will promise to advocate the concept internally. The strange coincidence is that the engineering director and many of the talented team behind DxDesigner and ICT now were previously responsible for the genesis of HDL Designer so the concept will not be foreign to them.

                    • 7. Re: Design entry, does it meet your needs?


                      At this point in time I will have to say that most schematic packages do and do not meet my needs.


                      Once upon a time I deeply believed in the idea of adding detailed constraints at the schematic level. For example, setting up diff pairs, net width and spacing rules, classes...etc...

                      I have since abandoned this belief as schematic packages have not made it easier over the years to do this and PCB packages have made huge improvements. Also, in my opinion, it is better

                      to do all this on the PCB side anyway's since many times you do not know that far in advance how your rules will work out. Since my shift in ideology I have to say that schematic packages meet my need.

                      They all make readable drawings, manage part libs, generate BOM's and create netlists, though there is one program I like better than the rest.



                      One area where they do not meet my needs is on the drafting side. Most schematic packages have poor drafting capabilities. It is sometimes necessary to have semi-detailed drawn

                      objects in your schematic and for the exception of the now deceased P-CAD, none of them are very good at this. It is unfortunate for me that my favorite program has the worst drafting tools of all.






                      • 8. Re: Design entry, does it meet your needs?

                        Hello Gary,



                                In the schematic point of view the design entry works well for the circut designeres ,we can give the net property ,buses length ,BOM creation e.t.c ,But it will not drive as any intelligent data for placement and layout ,Eventhough we grouped the design in schematics it scattered in layout when importing this in CAD file, If we can add some useful intelligent method in schematic itself the layout can be easily for designers .


                                I am going to write my suggestion here,I am not sure any tool is available for  fullfilling this,Suppose we have the three different sections in schematic like power supply  ,Analog and Digital section .

                        Fist we need to draw each different section in seperate room in schematics. When importing to netlist in CAD the components in particular room need to be arranged  and routed automatically with respect to

                        schematics wire assignment property ,Thus we can reduce many manual process for placement and shortest track ,when the user gives another click on particular room we need to get different placement and routing model for each click.So designers can select the good layout model for particular room





                        Sabitha Jamal