Answers Database
M1.3/M1.4 MAP: unclear messages about FDCEs being "covered by optimization" in the MAP .mrp file when the -os option is specified
Record #2758
Product Family: Software
Product Line: FPGA Implementation
Product Part: map
Product Version: 1.4.
Problem Title:
M1.3/M1.4 MAP: unclear messages about FDCEs being "covered by optimization" in the MAP .mrp
file when the -os option is specified
Problem Description:
Keyword: map, optimization, cover
Urgency: Standard
When running map with the -os speed option in M1.3.7, one may get messages of the type, "FF (FDCE) w
as covered by
optimization" in the map.mrp report:
"c0/c1/inst_slotsequencer/inst_dispatch/addr1_reg<10>" (FDCE) was covered by optimization.
"c0/c1/inst_slotsequencer/inst_dispatch/addr1_reg<11>" (FDCE) was covered by optimization.
The meaning of such messages may not be clear.
Reference #: 100637
Solution 1:
This message usually appears when the user uses the -os
option in Map. The -os option causes Map to invoke the OPTX
optimizer. One workaround is to not specify the option when
running Map.
The message does not mean that the components have been trimmed out. It means that the FFs specified
are located
in CLBs whose logic has been optimized.
When OPTX changes a CLB, it places it in a mapper structure called a GROUP. Any other logical elemen
ts that get combined with the logical elements of a given GROUP also become
members of that GROUP.
When Map reports on logic in a GROUP, it reports on ALL elements in the GROUP. So when Map issues t
he message, "FFs
(FDCE) are covered by optimization", it is reporting that
the flip-flops are part of that group, possibly having been
merged into the GROUP in the process of optimizing
the design.
If the design has already been optimized by a synthesis tools such as Synopsys, you should not be us
ing the -os
optimization switch.
Please refer to (Xilinx Solution 2680)
for guidance on when the -os switch should be used.
End of Record #2758 - Last Modified: 10/07/97 23:28 |
