Re: Design fits XC9536 but not XC9536XL

: Your design should fit going from the 9500 to the 9500xl. The 9500xl
: actually has more function block fanin (36 to 54!) so I would think
: that there should be no fitting issues.

That's what I hoped, but no luck (so far).

: The loss of wire-anding would cause your PTerm requirements to
: increase. Perhaps if you were near the maximum utilization for this it
: would not fit.

I suspect that is it.  The report I get from the failed XC9536XL fit is:

"Mapping a total of 36 equations into 2 function blocks......
 ERROR:Cpld:935 - Cannot place signal P<3>.  Consider reducing
 the collapsing input limit or the product term limit to prevent
 the fitter from creating high input and/or high product term
 functions".

When successfully put into an XC9536 the report says:

 Macrocells used:            36/36 (100%)
 Product terms used:       146/180 (81%)
 Registers used:             36/36 (100%)
 Pins used:                  34/34 (100%)
 Function block inputs used: 56/72 (77%)

There are lots of signals shown as "wire-AND input".

: You may want to try contacting the Xilinx hotline. They are willing to
: try fitting close designs.

I'll try that.

Richard.
http://www.rtrussell.co.uk /

 If the fitter has not at this stage reported the Prod terms, you
could re-target a 9572XL,(just for the purposes of getting
a complete fitter report!), and then compare with the one below.
 
 It's common for fitter reports to be sparse/terse on failure, so
you are sometimes best to use a 'does fit' pathway
- even if that needs some gyrations ! :)

-jg
 

A problem here, is it did not fit, and so you do not know if 180 is
product terms WANTED, or just the ceiling it bumped into.
 I can give you the observation 'It's not looking good' :)
-jg

: I would expect it to fit. Anything you can do in 2 logic blocks of
: 36V18 can be done in two 54V18.

: I would suggest to place the design into 9536 without XL, save the
: fitter report, run the fitter on 9536XL and compare fitter reports.

The big difference is that the XC9536 report has the 'wire-AND'
option enabled and the XC9536XL has it disabled.  My design makes
heavy use of the 'wire-AND' facility, and it has been suggested
that this is not available on the XC9536XL.  Is that correct ?

I have raised a Webcase on this issue, but no results so far.

Richard.
http://www.rtrussell.co.uk /

snipped-for-privacy@rtrussell.co.uk wrote in message


XC9500 uses FASTCONNECT switch matrix that is documented to have
wired-AND capability. XC9500XL uses FASTCONNECT II switch matrix that
doesn't have it documented, so I would think it's not there. The only
option is to use pin-compatible XC9572XL part, I guess...