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Constraint Blocks
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In last few pages we saw how to contraint a random variable to legal range that we want to generate. In next few pages we will see. |
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- inclusive and exclusive (set membership)
- distribution
- conditional constraint
- foreach
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And also some advanced constraint topics. |
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Set Membership
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Sometimes we want to randomize a variable within a set of values (inclusive) or sometimes we want to exclude some values from random values generated (exclusive). |
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- [] is used for specifying range.
- The negated form of the inside operator denotes that expression lies outside the set: !(expression inside { set }).
- Absent any other constraints, all values (either single values or value ranges) have an equal probability of being chosen by the inside operator.
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Example : Set Membership
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1 program set_membership;
2 class frame_t;
3 rand bit [7:0] src_port;
4 rand bit [7:0] des_port;
5 constraint c {
6 // inclusive
7 src_port inside { [8'h0:8'hA],8'h14,8'h18 };
8 // exclusive
9 ! (des_port inside { [8'h4:8'hFF] });
10 }
11 function void post_randomize();
12 begin
13 $display("src port : %0x",src_port);
14 $display("des port : %0x",des_port);
15 end
16 endfunction
17 endclass
18
19 initial begin
20 frame_t frame = new();
21 integer i,j = 0;
22 for (j=0;j < 4; j++) begin
23 $display("-------------------------------");
24 $display("Randomize Value");
25 $display("-------------------------------");
26 i = frame.randomize();
27 end
28 $display("-------------------------------");
29 end
30 endprogram
You could download file set_membership.sv here
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Simulation Output : Set Membership
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-------------------------------
Randomize Value
-------------------------------
src port : 3
des port : 2
-------------------------------
Randomize Value
-------------------------------
src port : 0
des port : 2
-------------------------------
Randomize Value
-------------------------------
src port : 18
des port : 3
-------------------------------
Randomize Value
-------------------------------
src port : 2
des port : 0
-------------------------------
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Copyright © 1998-2014 |
Deepak Kumar Tala - All rights reserved |
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Do you have any Comment? mail me at:deepak@asic-world.com
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