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AR# 56994

Does the Vivado Simulator support the 'driving_value VHDL system task?

Description

Does the Vivado Simulator support the 'driving_value VHDL system task?

Solution

The Vivado Simulator does not support the use of the VHDL 'driving_value system task.

The 'driving_value system task is used to determine the latest value being driven onto a signal by its driver within a given process.

The signal may or may not have actually been updated with the latest driving value due to delta delays present in all simulation tools.

In addition, this attribute is not supported in synthesis, so its use is not encouraged.

If necessary, the 'driving value can be approximated by using temporary variables as shown in the example below:

Unsupported Use Example:

        if S'driving_value = '1' then
            out1 <= in1;
        else
            out1 <= not in1;
        end if;

Supported Use Example:

        immediate_S := '1';
        S <= immediate_S;

        if immediate_S = '1' then
            out1 <= in1;
        else
            out1 <= not in1;
        end if;


Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
58882 Xilinx Simulation Solution Center - Design Assistant - Vivado Simulator - Behavioral Simulation N/A N/A
AR# 56994
Date Created 08/05/2013
Last Updated 01/28/2015
Status Active
Type General Article
Tools
  • Vivado Design Suite