How do you write a case statement in Verilog?
A Verilog case statement starts with the case keyword and ends with the endcase keyword. The expression within parantheses will be evaluated exactly once and is compared with the list of alternatives in the order they are written and the statements for which the alternative matches the given expression are executed.
What is a case statement in Verilog?
The case statement checks if the given expression matches one among the other expressions inside the list and branches. In Verilog, a case statement includes all of the code between the Verilog keywords, case (“casez”, “casex”), and endcase. …
What is hot encoding Verilog?
One-hot refers to how each of the states is encoded in the state vector. In a one-hot state machine, the state vector has as many bits as number of states. Each bit represents a single state, and only one bit can be set at a time—one-hot.
What is a one-hot state machine?
One-hot encoding is often used for indicating the state of a state machine. A ‘one-hot’ implementation would have 15 flip flops chained in series with the Q output of each flip flop connected to the D input of the next and the D input of the first flip flop connected to the Q output of the 15th flip flop.
What is Verilog Case 1 )?
In Verilog, a case expression can either be a constant, such as “1’b1” (one bit of ‘1’, or “true”), it can be an expression that evaluates to a constant value, or most often it is a bit or vector of bits that are used to compare against case items.
How do you write if else statements in Verilog?
This conditional statement is used to make a decision on whether the statements within the if block should be executed or not. If there is an else statement and expression is false then statements within the else block will be executed.
What is difference between one-hot and binary encoding?
Each bit of state is stored in a flip-flop, so one-hot encoding requires more flip-flops than binary encoding. However, with one-hot encoding, the next state and output logic is often simpler, so fewer gates are required. The best encoding choice depends on the specific FSM.
What is hot encoding in VLSI?
In one-hot encoding only one bit of the state vector is asserted for any given state. All other state bits are zero. Thus if there are n states then n state flip-flops are required. As only one bit remains logic high and rest are logic low, it is called as One-hot encoding.
What is a one-hot state assignment?
One-hot encoding is an alternative state assignment method which attempts to minimize the combinational logic by increasing the number of flip-flops. The goal of the method is to try to reduce the number of connections between the logic gates in the combinational circuit of the FSM.
Why is it called one-hot?
It is called one-hot because only one bit is “hot” or TRUE at any time. For example, a one-hot encoded FSM with three states would have state encodings of 001, 010, and 100. Each bit of state is stored in a flip-flop, so one-hot encoding requires more flip-flops than binary encoding.
Is Casex synthesizable Verilog?
Both casex and casez are synthesizable. Casex generates a don’t-care space for unspecified state points.
What is Casex and casez statement?
The case, casex and casez all do bit-wise comparisons between the selecting case expression and individual case item statements. casex ignores any bit position containing an X or Z; casez only ignores bit positions with a Z. Verilog literals use the both the? and z characters to represent the Z state.