Passing Parameters
As in any programming language, we can pass parameters to function. In this case methods. Passing of parameters can be donw with one of the following ways
- Scalar Parameter Passing
- Compound Parameter Passing
Scalar Parameter Passing
| Scalar parameters include numeric, Boolean, and enumerated types. When you pass a scalar parameter to a method, by default the value of the parameter is passed, this is same as in other programming language. |
1 <'
2 struct scoreboard {
3 ! mem_list : list of int;
4 // This method uses one input parameter
5 add_item (addr : int) is {
6 mem_list.push(addr);
7 };
8 // This method does not have any input
9 // parameters
10 print_sb () is {
11 print mem_list;
12 };
13 };
14 // Extend sys to run the simulate above methods
15 extend sys {
16 U_sb : scoreboard;
17 run() is also {
18 U_sb.add_item(10);
19 U_sb.add_item(22);
20 U_sb.print_sb();
21 };
22 };
23 '>
mem_list =
0. 10
1. 22
Compound Parameter Passing
Sometimes we may want to pass lot of parameters to a methods. Instead of typing each and every parameter, we can create a struct and pass this struct as parameter. Once again this is same as in C or C++. We can also pass a list as parameter to a method.
1 <'
2 struct mem_base_object {
3 addr : int;
4 data : int;
5 cmd : bool;
6 };
7
8 struct mem_txgen {
9 ! base_object : mem_base_object;
10 num_cmds : int;
11 // This methods the commands
12 gen_cmds () is {
13 var i : int = 0;
14 for i from 1 to num_cmds do {
15 // gen commands
16 gen base_object;
17 // Print the commands
18 print_cmds(base_object);
19 };
20 };
21 // This method prints the command details
22 print_cmds (cmd_struct : mem_base_object) is {
23 out ("Following command is generated");
24 outf(" Address : %x\n",cmd_struct.addr);
25 outf(" Date : %x\n",cmd_struct.data);
26 if (cmd_struct.cmd) {
27 out(" CMD : Read");
28 } else {
29 out(" CMD : Write");
30 };
31 };
32 };
33 // Extend sys to run the simulate above methods
34 extend sys {
35 txgen : mem_txgen;
36 keep txgen.num_cmds == 2;
37 run() is also {
38 txgen.gen_cmds();
39 };
40 };
Following command is generated
Address : 87abfa57
Date : af6d7f9
CMD : Read
Following command is generated
Address : f49771af
Date : 827afe11
CMD : Read
Passing By Reference
As in the C and C++, we can pass a parameter as reference, in this case what happens is if the variable is modified inside the method, the value gets reflected in global variable also. This is applicable to both Compound parameter passing and also to scalar parameter passing.
1 <'
2 struct counter_struct {
3 ! count_var : int;
4 // Counter
5 counter () is {
6 var i : int = 0;
7 for i from 0 to 10 do {
8 increment(count_var); // There is no * here
9 outf("Current value of count : %x\n",count_var);
10 };
11 };
12 // This method increments the passed parameter
13 // * is for the data type and not to variable
14 increment (count_passed : *int) is {
15 count_passed = count_passed + 1;
16 };
17 };
18 // Extend sys to run the simulate above methods
19 extend sys {
20 U_c : counter_struct;
21 run() is also {
22 U_c.counter();
23 };
24 };
25 '>
Current value of count : 1
Current value of count : 2
Current value of count : 3
Current value of count : 4
Current value of count : 5
Current value of count : 6
Current value of count : 7
Current value of count : 8
Current value of count : 9
Current value of count : a
Â
Current value of count : b
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