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Behaviotal Modeling part 3

[ Team LiB ] 7.3 Timing Controls Various behavioral timing control constructs are available in Verilog. In Verilog, if there are no timing control statements, the simulation time does not advance. Timing controls provide a way to specify the simulation time at which procedural statements will execute | Team LiB 7.3 Timing Controls Various behavioral timing control constructs are available in Verilog. In Verilog if there are no timing control statements the simulation time does not advance. Timing controls provide a way to specify the simulation time at which procedural statements will execute. There are three methods of timing control delay-based timing control event-based timing control and level-sensitive timing control. 7.3.1 Delay-Based Timing Control Delay-based timing control in an expression specifies the time duration between when the statement is encountered and when it is executed. We used delay-based timing control statements when writing few modules in the preceding chapters but did not explain them in detail. In this section we will discuss delay-based timing control statements. Delays are specified by the symbol . Syntax for the delay-based timing control statement is shown below. delay3 delay_value delay_value delay_value delay_value delay2 delay_value delay_value delay_value delay_value unsigned_number parameter_identifier specparam_identifier mintypmax_expression Delay-based timing control can be specified by a number identifier or a mintypmax_expression. There are three types of delay control for procedural assignments regular delay control intra-assignment delay control and zero delay control. Regular delay control Regular delay control is used when a non-zero delay is specified to the left of a procedural assignment. Usage of regular delay control is shown in Example 7-10. Example 7-10 Regular Delay Control define parameters parameter latency 20 parameter delta 2 define register variables reg x y z p q initial begin x 0 no delay control 10 y 1 delay control with a number. Delay execution of y 1 by 10 units latency z 0 Delay control with identifier. Delay of 20 units latency delta p 1 Delay control with expression y x x 1 Delay control with identifier. Take value of y. 4 5 6 q 0 Minimum typical and maximum delay values. Discussed in gate-level