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AR# 62702

Design Assistant for Vivado Synthesis - Help with Synthesis HDL Attribute Support - DIRECT_ENABLE,DIRECT_RESET

Description

This answer record describes the Vivado Synthesis Attributes DIRECT_ENABLE and DIRECT_RESET, and also provides coding examples for them.

The coding examples are attached to this answer record. The answer record also contains information related to known issues and good coding practices.

Note: Each coding example can be used to directly create a Vivado project.

Please refer to the header in each source file for the Synthesis attributes covered in each example.

Solution

DIRECT_ENABLE

The DIRECT_ENABLE attribute can be applied on an input port or other signal to have it go directly to the enable line of a flop when there is more than one possible enable.

The DIRECT_ENABLE attribute can be placed on any port or signal.

Verilog Example

(* direct_enable = yes *) input ena3;

VHDL Example

entity test is port(

in1 : std_logic_vector (8 downto 0);

clk : std_logic;

ena1, ena2, ena3 : in std_logic

out1 : std_logic_vector(8 downto 0));

attribute direct_enable : string;

attribute direct_enable of ena3: signal is "yes";

end test;




DIRECT_RESET

The DIRECT_RESET attribute can be applied on an input port or other signal to have it go directly to the reset line of a flop when there is more than one possible enable.

The DIRECT_RESET attribute can be placed on any port or signal

Verilog Example

(* direct_reset = "yes" *) input rst3;

VHDL Example

entity test is port(

in1 : std_logic_vector (8 downto 0);

clk : std_logic;

rst1, rst2, rst3 : in std_logic

out1 : std_logic_vector(8 downto 0));

attribute direct_reset : string;

attribute direct_reset of rst3: signal is yes;

end test;

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
55160 Design Assistant for Vivado Synthesis - Help with Synthesis HDL Attribute Support N/A N/A
AR# 62702
Date Created 11/04/2014
Last Updated 09/30/2016
Status Active
Type General Article
Tools
  • Vivado Design Suite - 2014.3