Sage-Tips

How is for loop synthesizable in Verilog?

Verilog for-loops are perfectly synthesizable under certain conditions:

• You can use any procedural statement within a loop (e.g. if-else).
• The number of loops must be predetermined.
• You can assign a different value to the same variable in each loops (e.g. calculating an index from the loop variable).

Why for loop is not synthesizable in Verilog?

It is not synthesizable. The number of times that the for loops is not known at compile time. Recall that the for condition has tmp , which is initialized with data whose value we don’t know at compile time. In order for this code (or any other) to be synthesizable, the compiler must be able to unroll the loop.

How do you use a HDL loop?

The for loop statement is used when a discrete range can define the number of iterations. In the header of the loop the discrete range for the loop parameter is specified. In each iteration the parameter takes one value from the specified range, starting from the leftmost value within the range.

HOW DO FOR loops work in VHDL?

In VHDL the FOR-LOOP statement is a sequential statement that can be used inside a process statement as well as in subprograms. The FOR-LOOP statement is used whenever an operation needs to be repeated.

Is repeat loop synthesizable in Verilog?

Repeat Loops can be used synthesizable code, but be careful with them!. They should only be used to expand replicated code. More often, repeat loops are used in testbenches. Note that the Jump Statements return and break can be used to exit your loop prematurely, but these are only supported in SystemVerilog.

What does a for loop do in synthesizable code?

For loops in synthesizable code are used for expanding replicated logic. They are simply a way of shrinking the amount of code that is written by the hardware designer. They do not loop like a C program loops. They only expand replicated logic.

What is synthesizable and non-synthesizable in Verilog?

Synthesizable Verilog is that subset of the language that are accepted by the synthesis tools. The non-synthesizable constructs are used only for simulation and the synthesis tool cannot handle them.

What is synthesizable and non-synthesizable?

For something to be synthesizable it has to be able to be represented in hardware, i.e. using logic gates. An example of something that is non-synthesizable would be initializing a design with values assigned to signals or registers. This cannot be translated to hardware, therefor is non-synthesizable.

How does for loop work in Verilog?

Verilog For Loop. When writing verilog code, we use the for loop to execute a block of code a fixed number of times. As with the while loop, the for loop will execute for as long as a given condition is true. The specified condition is evaluated before each iteration of the loop.

Is repeat synthesizable in Verilog?

Repeat Loops can be used synthesizable code, but be careful with them!. They should only be used to expand replicated code.

Are for loops synthesizable in VHDL?

For loops can be used in both synthesizable and non-synthesizable code. However for loops perform differently in a software language like C than they do in VHDL. You must clearly understand how for loops work before using them!

Is always block synthesizable in Verilog?

Embedded always blocks are not synthesizable. Adding timing delays would not be synthesisable, but often used in verification. Also some tools will complain if you try to synthesise display statements.