AR# 3766: MAP M1.4: x4kma:312 - The following symbols could not be constrained to a single CLB (Two F-LUT's, an H-LUT, and carry logic).
MAP M1.4: x4kma:312 - The following symbols could not be constrained to a single CLB (Two F-LUT's, an H-LUT, and carry logic).
Keywords: MAP, legal, pack, constrain, CLB
This solution record involves one case where the following error message is encountered during MAP.
----- ERROR: x4kma:312 - The following symbols could not be constrained to a single CLB: CY4 symbol "$1I243" (output signal=C6) CY4_12 symbol "$1I196" (output signal=$1N232) FMAP symbol "$1I221" (output signal=S6) HMAP symbol "$1I345" (output signal=S7) FMAP symbol "$1I222" (output signal=S) There are two resources that require the F function generator. These symbols share the same RLOC attribute value, which requires them to be mapped to the same CLB. -----
In this specific case, all three lookup tables and the carry logic are being utilized. The carry mode is ADDSUB. The CIN input is driven and also goes to the F-LUT. The carry goes to the G-LUT. The F-LUT utilizes all four inputs and the output goes out of the CLB. The G-LUT uses all four inputs. The H-LUT has all three inputs driven: one comes from the output of the G-LUT, and the other two from outside the CLB. The H-LUT output goes out of the CLB. This looks to be a legal pack.
MAP M1.4 cannot perform this legal CLB pack. It has been addressed and fixed for the next Core Tools release, M1.5.