Besides, Verilog has a single always block to implement combinational and sequential logic while SystemVerilog has alwayscomb, alwaysff and alwayslatch procedural blocks. While Verilog is based on a hierarchy of modules, SystemVerilog is based on classes. Additionally, Verilog uses module level testbench while. Verilog is based on module level testbench. SystemVerilog is based on class level testbench. It is standardized as IEEE 1364. It is standardized as IEEE 1800-2012. Verilog is influenced by C language and Fortran programming language. SystemVerilog is based on Verilog, VHDL and c programming language. It has file extension.v or.vh. We introduce a SystemVerilog unit testing framework from AgileSoC called SVUnit. We show how to create example SVUnit tests to test a Verilog module.
Formal Definition
Module instantiation provides a means of nesting modules descriptions.
Simplified Syntax
module_name [parameter_value_assignment] module_instance ;
Description
Modules can be instantiated from within other modules. When a module is instantiated, connections to the ports of the module must be specified. There are two ways to make port connections. One is connection by name, in which variables connected to each of module inputs or outputs are specified in a set of parenthesis following the name of the ports. In this method order of connections is not significant. See Example 1.
The second method is called ordered connection. In this method the order of the ports must match the order appearing in the instantiated module. See Example 2. When ports are connected by name it is illegal to leave any ports unconnected. This may occur when ports are connected by order. See Example 3.
What happens if you leave a port unconnected depends on the type of the port. If you are connecting net type ports, unconnected bits are driven with high impedance. In other cases, bits are driven with unknown values. Akuma demon spawn free download.
Module instantiations can create an array of instances. To create theses instances, range specifications have to be declared after the module name. The array of instances can save you time in writing code and provide a way to enrich your readability, see Example 4
Examples
Example 1
module dff (clk, d, q);
input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
module top;
reg data, clock;
wire q_out, net_1;
dff inst_1 (.d(data), .q(net_1), .clk(clock));
dff inst_2 (.clk(clock), .d(net_1), .q(q_out));
endmodule
In the top module there are two instantiations of the 'dff' module. In both cases port connections are done by name, so the port order is insignificant. The first port is input port 'd', the second is output 'q' and the last is the clock in the 'inst_1'. In the dff module the order of ports is different than either of the two instantiations.
Example 2
module dff (clk, d, q);
input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
module top;
reg data, clock;
wire q_out, net_1;
dff inst_1 (clock, data, net_1);
dff inst_2 (clock, net_1, q_out);
endmodule
Example 3
dff inst_1 (clock, , net_1);
Second port is unconnected and has the value Z because it is of the net type. Izotope ozone 5 reddit.
Example 4
module my_module (a, b, c);
input a, b;
output c;
assign c = a & b ;
endmodule
module top (a, b, c) ;
input [3:0] a, b;
output [3:0] c;
my_module inst [3:0] (a, b, c);
endmodule
Important Notes
If ports are connected by name it is illegal to leave any ports unconnected.
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(30)Without using randomize method or rand,generate an array of unique values?
Ans:-
(32)What is the difference between byte and bit [7:0]?
Ans:-
byte is signed whereas bit [7:0] is unsigned.
(33)What is the difference between program block and module?
Ans:-
Program block is newly added in SystemVerilog. It serves these purposes
- It separates testbench from DUT
- It helps in ensuring that testbench doesn't have any race condition with DUT
- It provides an entry point for execution of testbench
- It provides syntactic context (via program .. endprogram) that specifies scheduling in the Reactive Region.
- Program blocks can't have always block inside them, modules can have.
- Program blocks can't contain UDP, modules, or other instance of program block inside them. Modules don't have any such restrictions.
- Inside a program block, program variable can only be assigned using blocking assignment and non-program variables can only be assigned using non-blocking assignments. No such restrictions on module
- Program blocks get executed in the re-active region of scheduling queue, module blocks get executed in the active region
- A program can call a task or function in modules or other programs. But a module can not call a task or function in a program.
- http://www.project-veripage.com/program_blocks_1.php and few more next/next !!!
- Section 16, SystemVerilog LRM 3.1a .. It's worth the effort reading line-by-line (and between the lines if you can :) ).
Ans:-
Program Block Vs Module Systemverilog
Modports are part of Interface. Modports are used for specifing the direction of the signals with respect to various modules the interface connects to.For Loop In Systemverilog
Please refer section 19.4 of SV LRM for more details
11. Explain about the virtual task and methods .
Ans:-
See http://www.testbench.in/CL_07_POLYMORPHISM.html