SRL_STYLE instructs the synthesis tool on how to infer SRLs that are found in the design. Accepted values are:
•register: The tool does not infer an SRL, but instead only uses registers.
•srl: The tool infers an SRL without any registers before or after.
•srl_reg: The tool infers an SRL and leaves one register after the SRL.
•reg_srl: The tool infers an SRL and leaves one register before the SRL.
•reg_srl_reg: The tool infers an SRL and leaves one register before and one register after the SRL.
•block: The tool infers the SRL inside a block RAM.
Place SRL_STYLE on the signal declared for SRL. This attribute can be set in RTL and in XDC. The attribute can only be used on static SRLs. The indexing logic for dynamic SRLs is located within the SRL component itself. Therefore, the logic cannot be created around the SRL component to look up addresses outside of the component.
CAUTION! Use care when using combinations of SRL_STYLE, SHREG_EXTRACT, and -shreg_min_size. The SHREG_EXTRACT attribute always take precedence over the others. If SHREG_EXTRACT is set to "no" and SRL_STYLE is set to "srl", registers are used. The -shreg_min_size, being the global variable, always has the least amount of precedence. If an SRL of length 10 is set and SRL_STYLE is set to "srl" and -shreg_min_size is set to 20, the SRL is still inferred.
Note: In the examples below, the SRLs are all created with buses where the SRL is shifting from one bit to the next. If the code that is to use SRL_STYLE has many differently named signals driving each other, then place SRL_STYLE attribute on the last signal in the chain. This includes if the last register in the chain is in a different level of hierarchy than the other registers. The attribute always goes on the last register in the chain.