Answers Database

PPR issues ERROR 6105 due to incorrect FMAP for XBLOX ACCUM


Record #950

Product Family:  Software

Product Line:  FPGA Core

Problem Title:
PPR issues ERROR 6105 due to incorrect FMAP for XBLOX ACCUM


Problem Description:
PPR gives the following error while it is trying to map an XBLOX accumulator:

*** PPR: ERROR 6105:
	  The MAP symbol '$1I1_1/FMAP8_1_1_3' (output signal=$1I1_1/SUM<3>) can
	  not be obeyed.
	  The following input signals are specifiled on the MAP symbol:
	  $1I1_1/MUX_SEL_1_3
	  $1I1_1/CO_3
	  XIN<3>
	  However, the gates that generate the signal $1I1_1/SUM<3> have the
	  following input signals:
	  $1I1_1/MUX_SEL_1_3
	  $1I1_1/CO_3
	  Check that the input and output signals assigned to the MAP completely

	  enclose the intended logic.

This error occurs because XBLOX did not generate correct FMAPs for the
synthesized ACCUM logic.  When the ACCUM component is only using the ADD
functionality, it is not necessary to generate the FMAP in question, but
XBLOX generates the FMAP for the fully functional ACCUM even though the
corresponding logic only doesn't require it.  This mismatch causes a PPR
error because the FMAP does not correspond to the logic being implemented.


Solution 1:

Add a USE_RLOC=FALSE attribute to the ACCUM symbol.  This will force XBLOX
not to generate an RPM for that specific XBLOX symbol.	Note that this may
adversely affect performance, as it will also prevent XBLOX from using the
dedicated carry logic.



End of Record #950