Stratix® IV FPGA ALM Logic Structure's 8-Input Fracturable LUT

Table 1. Stratix IV FPGA ALM Configurations

Configuration

Description

6-LUT

One Stratix IV ALM can support any 6-input logic function.

4-LUT

4-LUT

One Stratix IV ALM can be configured to implement two independent 4-input or smaller LUTs.

5-LUT

3-LUT

One Stratix IV ALM can be configured to implement a 5-input LUT and a 3-input LUT. The inputs to the two LUTs are independent of each other. The 3-LUT can be used to implement any logic function that has three or fewer inputs. Therefore, a 5-input LUT and 2-input LUT combination is also available.

5-LUT

4-LUT

One Stratix IV ALM can be configured to implement a 5-input LUT and a 4-input LUT. One of the inputs is shared between the two LUTs. The 5-input LUT has up to four independent inputs. The 4-input LUT has up to three independent inputs. The sharing of inputs between LUTs is very common in FPGA designs, and the Quartus Prime software automatically seeks logic functions that are structured in this manner.

5-LUT

5-LUT

One Stratix IV ALM can be configured to implement two 5-input LUTs. Two of the inputs between the LUTs are common, and up to three independent inputs are allowed for each 5-input LUT.

6-LUT

6-LUT

If two 6-input functions have the same logic operation and four shared inputs, then the two 6-input functions can be implemented in one Stratix IV device ALM.

7-LUT

One Stratix IV device ALM in the extended mode can implement a subset of a 7-variable function. The Quartus Prime software automatically recognizes the applicable 7-input function and fits it into an ALM.