maxfan VHDL Synthesis Attribute

A VHDL synthesis attribute that directs Analysis & Synthesis to duplicate a register to ensure that the register's fan-out does not exceed the maximum value you specify. You can use this option to reduce the load of critical signals in the design, thereby improving performance.

Use an Attribute Declaration and Attribute Specifications to use the maxfan synthesis attribute in a design. You must associate the maxfan synthesis attribute only with registers, and you must specify the maximum value of fan-out an associated register can have. For example, in the following code, the Attribute Declaration declares the maxfan synthesis attribute, and the Attribute Specification associates the maxfan synthesis attribute with the clkgen register and specifies that the register have a maximum of 200 fan-outs:

SIGNAL clk_gen : STD_LOGIC; ATTRIBUTE maxfan : INTEGER ; ATTRIBUTE maxfan OF clk_gen : SIGNAL IS 200;