> Create more coefficient generators and sprinkle them around inside the > PFB? > > Sorry, I don't have Simulink with me, so can't offer more concrete > advice. But if the problem is with the fanout, why not create seperate > sources with smaller fanouts?
There are separate coefficient generators for every path in the library block, but they seem to get optimized out during the build. That's the trick, I guess, that I don't know how to get around... Thanks John > > Jason > > > On 06 Nov 2008, at 15:46, John Ford wrote: > >> Does anyone have any suggestions for fixing this error? It seems due >> entirely to the large fanout (450!) in the coefficient generator. >> >> We're stuck on this for building our 4K channel 800 MHz pulsar >> machine. >> It is introducing errors into the spectrum. >> >> John >> >> >>> Hi all. Here's a timing error that appears when building a large >>> (2^^3 >>> parallel paths, 2^^13 points, 4 taps 7 bit coefficients, 7 bit >>> input, 14 >>> bit output) PFB. The timing wizard's suggestions are below. Note >>> that >>> the coeff. generator counter seems to be used for all coeff generator >>> counters in the entire PFB's complement of coeff generators. >>> >>> How can I tell the toolset not to optimize out all the other >>> counters, or >>> alternatively, how can I introduce a delay to fix this problem? I've >>> attached the twx file, but from the timing wizard: >>> >>> This path has a net >>> "b2_gdsp_u1_8k_800_a_nb_xsg_core_config/ >>> b2_gdsp_u1_8k_800_a_nb_xsg_core_config/ >>> top/pfb_fir_real_4k_ch/pol1_in1_first_tap/pfb_coeff_gen/counter_q(4)" >>> with a high fanout of 450. >>> >>> High fanout suggestions. >>> >>> -Duplicate the net source and direct the synthesis tools not to >>> remove >>> duplicate logic. >>> >>> -Use a specific net fanout control on the problem net if allowed by >>> the >>> synthesis tool. >>> >>> Click Next button if this suggestion does not help. >>> >>> Thanks for any help! >>> >>> John >>> >>> >>> >> >> >> >
