register packing Definition

A feature that allows you to combine a register with a combinational function in the same logic cell, or to merge into I/O cells, RAM blocks, or DSP blocks. This option is useful for reducing logic element count in a design and improving performance.

It is essential to pack registers into the DSP blocks to achieve maximum performance. Refer to the Fixed Point DSP Register Packing Summary and Fixed Point DSP Register Packing Details Compilation Reports to determine where to implement register packing improvements.

Specify a value for the Auto Packed Registers logic option to direct the Compiler to automatically implement register packing for appropriate pairs of logic functions. Specify this logic option by clicking Assignments > Assignment Editor or by clicking Assignments > Settings > Compiler Settings > Advanced Settings (Fitter).

Alternatively, implement register packing manually by assigning a register and a combinatorial function to the same logic cell, or by assigning a register to an I/O cell, DSP block, or RAM block. However, for best results, use the Auto Packed Registers logic option to implement register packing automatically.