AR# 1810: M1.3 MAP: BLKNM, HBLKNM, RLOC and LOC Properties May Not be Respected by MAP in Some Instances
AR# 1810
M1.3 MAP: BLKNM, HBLKNM, RLOC and LOC Properties May Not be Respected by MAP in Some Instances
Description
Keywords: map blknm hblknm rloc loc
Urgency: hot
General Description:
Architecture(s): XC4000E/L/EX/XL, XC5200/L
Reference Numbers: 12904, 12934
MAP first maps logic based on FMAP/HMAP combinations before it tries to follow any user-specified BLKNM, HBLKNM, RLOC or LOC properties. MAP may therefore ignore user-specified properties like BLKNM, HBLKNM, RLOC or LOW.
When the properties are ignored, MAP will issue a warning similar to the following:
<OUTPUT> WARNING - Unable to combine AND2 symbol and BUF symbol </OUTPUT>
Solution
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Workarounds are design-specific:
If MAP is combining two LUTs (lookup tables, which includes FMAPs and HMAPs) into the same CLB, for example, one with BLKNM=fred, and the other with no BLKNM, and this is not what you want, you can prevent the combination by attaching a different BLKNM to the LUT that you do not want combined with the BLKNM=fred logic.
You should also attach X attributes to the nets that you want mapped as the external outputs of the logic you are trying to map into the CLB in question.
You may also try creating the desired configuration in EPIC, and converting it into a physical macro. This may then be instantiated into your design. For more information on creating physical macros, refer to the online (Xilinx Manual EPIC Design Editor Reference/User Guide)
If all else fails, you may have to manually remove the properties and allow MAP to operate without them.