18.104.22.168. Normal Mode
Normal mode allows two functions to be implemented in one Intel® Stratix® 10 ALM, or a single function of up to six inputs.
Up to eight data inputs from the LAB local interconnect are inputs to the combinational logic.
The ALM can support certain combinations of completely independent functions and various combinations of functions that have common inputs. The Intel® Quartus® Prime Compiler automatically selects the inputs to the LUT. ALMs in normal mode support register packing.
The following figure shows a combination of different input connections for the LUT mode. In your design, the Intel® Quartus® Prime software may assign different input namings during compilation.
Combinations of functions with fewer inputs than those shown are also supported. For example, combinations of functions with the following number of inputs are supported.
- 4 and 3
- 3 and 3
- 3 and 2
- 5 and 2
For the packing of two 5-input functions into one ALM, the functions must have at least two common inputs. The common inputs are dataa and datab. The combination of a 4-input function with a 5-input function requires one common input (either dataa or datab).
In a sparsely used device, functions that could be placed in one ALM may be implemented in separate ALMs by the Intel® Quartus® Prime software to achieve the best possible performance. As a device begins to fill up, the Intel® Quartus® Prime software automatically uses the full potential of the Intel® Stratix® 10 ALM. The Intel® Quartus® Prime Compiler automatically searches for functions using common inputs or completely independent functions to be placed in one ALM to make efficient use of device resources. In addition, you can manually control resource use by setting location assignments.
You can implement any three to six input function using the following inputs:
- dataa and datab—whereby dataa and datab are shared across both LUTs to provide flexibility to implement a different function in each LUT.
Both dataa and datab inputs support the register packing feature. If you enable the register packing feature, both dataa and datab inputs or either one of the inputs bypass the LUT and directly feed into the register, depending on the packed register mode used. For Intel® Stratix® 10 devices, the following types of packed register modes are supported:
- 5-input LUT with 1 packed register path
- Two 3-input LUTs with 2 packed register paths
The 3-input LUT with 2 packed register paths is illustrated in the 3-Input LUT Mode Function in Normal Mode figure. For Intel® Stratix® 10 devices, the 6-input LUT mode does not support the register packing feature.
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