What does X mean in modelsim?
x means the value of the signals is unknown; this is because the inputs have just been initialized, and the signals have not propagated through the module to the outputs.
What is the x value in a simulator?
“X” is used by simulators when a wire hasn’t been initialized to a known value or when the predicted value is an illegitimate logic value (e.g., due to contention on a tri-state bus).
What is X in VHDL?
X usually represents a net driven by multiple drivers. But in real life a multiply driven net will be at some voltage. That voltage is measured by the IO pin and is determined to be either 1 or 0. https://electronics.stackexchange.com/questions/458144/vhdl-what-will-happen-in-case-of-u-or-x-or-z-signal/458147#458147.
What does X mean in Xilinx?
Xilinx ISE Simulator assigns ‘X’ value to the output My project’s basic idea is that a clock signal samples another clock via a latch. My clocks have very close frequencies and both need to have jitter, so the sampling process occurs at the jitter zone and as a consequence of this, the output wil have a random value.
How do you use a floating scope?
Add Floating Scope Block to Model and Connect Signals
- Double-click the Floating Scope block.
- In the scope window toolbar, click the signal selection button .
- Select the signals you want to connect to the scope.
- In the Connect pop-up, select the check box next to the signals you want to connect.
What do you need to know about VHDL code?
In your VHDL code you described latches for the signals cancela and Ncarros as also reported by the “Analysis & Synthesis” step:
How are signal assignments resolved in ModelSim VHDL?
The signal assignments at the first place continuously assign “0000” to A and B. These are not an assignment of an initial value. Then your process assigns something to the same signals, thus, you have multiple drivers which are resolved.
What is the result of the testbench simulation?
However in the simulation results it shows ‘X’ for inputs which used to be ‘1’.Here is the result: And this is the Testbench: