184.108.40.206. Arithmetic Mode
The LE in arithmetic mode implements a two-bit full adder and basic carry chain. LEs in arithmetic mode can drive out registered and unregistered versions of the LUT output. Register feedback and register packing are supported when LEs are used in arithmetic mode.
The Intel® Quartus® Prime Compiler automatically creates carry chain logic during design processing. You can also manually create the carry chain logic during design entry. Parameterized functions, such as LPM functions, automatically take advantage of carry chains for the appropriate functions. The Intel® Quartus® Prime Compiler creates carry chains longer than 16 LEs by automatically linking LABs in the same column.
To enhanced fitting, a long carry chain runs vertically, which allows fast horizontal connections to M9K memory blocks or embedded multipliers through direct link interconnects. For example, if a design has a long carry chain in an LAB column next to a column of M9K memory blocks, any LE output can feed an adjacent M9K memory block through the direct link interconnect.
If the carry chains run horizontally, any LAB which is not next to the column of M9K memory blocks uses other row or column interconnects to drive a M9K memory block.
A carry chain continues as far as a full column.
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