Randomization in SV

SV builds the key concept of Testbench: the CRT (constraint random test), the randomization of the test set.

Because the object class consists of data and operations, randomization of the data is typically placed within a class. (The configuration of the environment or environment can also be reflected in the randomization of configuration parameters)

A constraint consists of two parts: RAND/RANDC variable declaration, constraint constraint block. Where RANDC is periodically evaluated before repetition, the variable in the constraint constraint block has at least one RAND/RANDC

Variable, the constraint constraint block must be used within {} to represent multiple constraints. A constraint block is a declarative code that runs in parallel.

Constraint: Typically referenced in a initial module or program, in the form of an assert: Assert (P.randomize ()); After randomization fails, the return value of 0,assert will print log.

and exit. There are also two hidden function:pre_randomize (), Post_randomize (), which can be added to the initialization of non-randomize variables while leaving a hook.

Several constraint modes:

1) Constraint Longth {Low < Mid;

Mid < High;} Relational operators must be written separately.

2) constraint length {len = = Mid-Low;} You cannot have assignment statements within a constraint block, instead you should use relational operators

3) constraint C_dist {src_dist {0:= 40, [1:3]:=60;} : = After---equal weight

dst_dist {0:/ 40, [1:3]:/   60};} :/Post Weight---scale

4) constraint C_rang {c inside {[Lo:hi]}; Inside:low-high

b inside {[10:$]}; $ can represent boundaries

! (c inside {[$:30]}); }//Plus () can be added! Represents a non-

5) Constraint C_io {(io_space_mode)--and Addr[31]==1 ' B1; ---> Indicates if

if (Op==read) len inside {[Byte:word]}; }//--->if--else

6) Constraint C_xy {(x==0), y==0; Solve. The probability that before may change the solution

Solve x before y;}

7) Assert (T.randmize () with {addr > 50; Inline constraints, the scope of addr is class at this level, the effect of randomize is equivalent

Addr < 150;} )

Switch control of the constraint:

Initial begin

p = new ();

P.c_short.constraint_mode (0); HANDLE + constraint block +mode, control this constraint block mode

ASSERT (P.randomize ());

Transmit (p);

P.contraint_mode (0); Handle +mode, control the entire handle of mode

P.c_short.constraint_mode (1);

ASSERT (P.randomize ());

Transmit (p);

End

Constraints on arrays:

1) constraint D_size {d.size inside {[1:10]};

D.sum = = 4 ' h4; The number of bits in the//sum is the same as the number of digits in the array, so you may not be able to reach the desired range.

In real-world applications, variables should be used to control constraints.

Randomization in SV