Archived ISE issues

[hoosha]

Hi!

Is is possible to describe a circuit with HDL and then turn it into a hard macro? If yes, how?

thanks,

Hooman 

[Chadn_na]

Yes you can create a Hard Macro, take a look at the FPGA Editor Help Guide from the link below, it has a whole section on macros:

http://toolbox.xilinx.com/docsan/xilinx10/help/iseguide/mergedProjects/fpga_editor/fpga_editor.htm

You can also to get this from the website by going to:
www.xilinx.com->Documentation->Design Tools Tab->ISE Foundation / ISE WebPACK->Select Preferred Version-> ISE Software Manuals

[hoosha · Accepted solution]

Yes thanks.

But what I really needed at that point was something like these:

http://www.xilinx.com/support/answers/10901.htm

and

http://www.soe.ucsc.edu/classes/cmpe225/Fall01/hardmacro.html

Message Edited by hoosha on 07-08-2008 05:28 AM

[blingerlive]

I noticed that in http://www.xilinx.com/support/answers/10901.htm, it states that using routed hard macros will increase your PAR time.  Why is that so?  Doesn't it need to do less work, since some of the circuit is already PARed. 

Also, will PAR move the macro as a contiguous unit around, and try to fit it in a location where it can legally go (i.e. all of the required routing wires, pips, and slices exists for that macro).

[adam123]

---

blingerlive wrote:

I noticed that in http://www.xilinx.com/support/answers/10901.htm, it states that using routed hard macros will increase your PAR time.  Why is that so?  Doesn't it need to do less work, since some of the circuit is already PARed. 

---

I can't speak for Xilinx's software specifically, but most routing algorithms work by picking a net that isn't yet routed, picking a route for it, and then "ripping up" any already-routed nets that use resources along that path.  The ripped-up routes are then put back in the set of nets to be routed.

When you have a hard macro, the router can't "rip up" any routes that are part of it.  So, I would guess, it just tries again.  If you've used too many routing resources in your hard macro, this process of repeatedly guessing might take a very long time (perhaps forever!).