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What is the difference between always and initial block in Verilog?
The difference between the two is that initial processes execute once, whereas always process execute repeatedly forever. As such, an always process must contain timing statements that will occasionally block execution and allow time to advance (time in initial and always process only advances when they are blocked).
What are the two Verilog procedural block types?
There are two types of procedural blocks in Verilog:
- initial : initial blocks execute only once at time zero (start execution at time zero).
- always : always blocks loop to execute over and over again; in other words, as the name suggests, it executes always.
Why do we use always in Verilog?
Uses of always block An always block can be used to realize combinational or sequential elements. A sequential element like flip flop becomes active when it is provided with a clock and reset. Similarly, a combinational block becomes active when one of its input values change.
When do you use always block in Verilog?
The always block indicates a free-running process, but the initial block indicates a process executes exactly once. Both constructs begin execution at simulator time 0, and both execute until the end of the block. Initial blocks can be used in either synthesizable or non-synthesizable blocks.
Why is initial ( Verilog ) statement is not synthesizable?
Why Initial (verilog) statement is not synthesizable?….. initial sentence is only used to verify our design,can not to describe the real circuit. In real circuit , there is a reset signal to initialize the signal. The “initial” statement is only behaviorl. not synthesisable. I disagree.
Why not use a wire with assign in Verilog?
For Xilinx FPGA designs, it is best not to use global reset lines, and use initial blocks for reset conditions for most logic. Here is the white paper from Ken Chapman (Xilinx FPGA guru) The always @* would never trigger as no Right hand arguments change. Why not use a wire with assign?
What can a synthesizable initial block be used for?
A synthesizable initial block is used to set the power-on value of registers, RAM, and ROM within FPGAs. However, initial blocks cannot be synthesized in ASICs or CPLDs.