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How do you avoid latches in Verilog?
To avoid this, make sure that all of your if statements that are used in combinational always blocks always have one last else statement to catch all missing conditions! Another place where a latch could be generated in Verilog is in a case statement that does not include the default assignment.
How is latch implemented in Verilog?
A latch can be implemented implicitly with Conditional (“If-Else”) Statements that have not been completely specified. The Conditional Statement must be inside an Always Construct that is not sensitive to a posedge or negedge clock. The example below shows a Verilog Design Files (.
What is meant by inferring latches how do you avoid it with an example?
A latch is inferred within a combinatorial block where the net is not assigned to a known value. Assign a net to itself will still infer a latch. Latches can also be inferred by missing signals form a sensitivity list and feedback loops.
Are latches synthesizable?
Latches are inferred only in combinatorial logic processes when there is an incomplete IF statement. This is due to the fact that an incomplete if statement requires the storage of information which is not possible with the simpler elements of combinatorial logic (wires and gates).
Where can a latch be generated in Verilog?
Another place where a latch could be generated in Verilog is in a case statement that does not include the default assignment. If not all possible cases are accounted for and the case is in a combinational always block then the synthesis tools will infer a latch.
How to avoid latches in your FPGA code?
Let’s look at one more example in Verilog: This code above will generate a latch, because the output o_latch is not defined when the input i_select is equal to 2’b11. To avoid this, make sure that all of your if statements that are used in combinational always blocks always have one last else statement to catch all missing conditions!
How to avoid latches in combinational always blocks?
To avoid this, make sure that all of your if statements that are used in combinational always blocks always have one last else statement to catch all missing conditions! Another place where a latch could be generated in Verilog is in a case statement that does not include the default assignment.
How to fix code that does not create latch?
To fix the code above, the Digital Designer can either specify what happens when i_select = “11” or can use the else clause with no when attached to it. I recommend the latter because it is more flexible. If the width of i_select changes from two bits to three bits your code will still not create a latch.