Ch5 Basic OOP

tr_gen tr_drv Stack
Static Varibles
class Transaction; static int count = 0; int id; function new(); id = count++; // Set ID, bump count endfunction endclass Transaction t1, t2; initial begin t1 = new(); // 1st instance, id=0, count=1 t2 = new(); // 2nd instance, id=1, count=2
transmit(t); $display("after t.display(); end endprogram transmit"); program testgen; task transmit(Transaction t); t.addr = t.addr << 2; endtask Transaction t; initial begin t = new(32'h0033); $display("before transmit"); t.display();
Modifying a Handle in a Task
class Transaction; logic [31:0] addr; function new(logic [31:0] addr); this.addr = addr; endfunction function void display(); $display(addr); endfunction endclass program testgen; task transmit(ref Transaction t); t = new(32’h3300); t.addr = t.addr << 2; endtask Transaction t; initial begin t = new(32'h0033); $display("before transmit"); t.display(); transmit(t); $display("after t.display(); end endprogram
There is a mistake in book “SystemVerilog for Verification, 2nd Edition” on page 147.
Modifying a Handle in a Task
class Transaction; logic [31:0] addr; function new(logic [31:0] addr); this.addr = addr; endfunction function void display(); $display(addr); endfunction endclass
tr_gen.display(); tr_drv.display(); end
ObjectName.Method
Classes can be used in programs and modules.
Handle and Object Constructor and Deallocation
Transaction tr_gen, tr_drv; tr_gen = new; tr_drv = tr_gen; tr_gen = new; tr_gen = null;
function Transaction::new(logic [31:0] addr); this.addr = addr; this.kind = ’x; this.data = ’x; endfunction: new function void Transaction::display(); $display(“addr=%h, kind=%b, data=%h”, addr, kind, data); endfunction: display
transmit");
Modifying Objects in Flight
// buggy generator task generator_bad(int n); Transaction t; t = new(); repeat (n) begin t.addr = $random(); transmit(t); end endtask // good generator task generator_bad(int n); Transaction t; repeat (n) begin t = new(); t.addr = $random(); transmit(t); end endtask
Arrays of Handles
class Transaction; logic [31:0] addr; function new(logic [31:0] addr = 'x); this.addr = addr; endfunction function void display(); $display("addr = %h", addr); endfunction endclass foreach(t[i]) begin t[i] = new(i); t[i].display(); end end endprogram program testgen; Transaction t[]; initial begin t = new[5];
Defining A Simple Class
class Transaction; logic [31:0] addr; logic kind; Property logic [63:0] data; function new(logic [31:0] addr); this.addr = addr; this.kind = ’x; this.data = ’x; endfunction function void display(); $display(“addr=%h, kind=%b, data=%h”, addr, kind, data); endfunction endclass Method Constructor Class
Ch5
Basic OOP
OOB Terminቤተ መጻሕፍቲ ባይዱlogy
Class – a basic building block containing routines and variables. The analogue in Verilog is a module. Object – an instance of a class. In Verilog, you need to instantiate a module to use it. Handle – a pointer to an object. In Verilog, you use the name of an instance when you refer to signals and methods from outside the module. An OOP handle is like the address of the object, but is stored in a pointer that can only refer to one type. Property – a variable that holds data. In Verilog, this is a signal such as a register or wire. Method – the procedural code that manipulates variables, contained in tasks and functions.Verilog modules have tasks and functions plus initial and always blocks. Prototype – the header of a routine that shows the name, type, and argument list. The body of the routine contains the executable code.
Method prototype must match the one in the body.
Using One Class Inside Another
//normal order class Statistics; ... endclass class Transaction; Statistics stats; ... endclass class Statistics; ... endclass class Transaction; Statistics stats; ... endclass //use a undefined class typedef class Statistics;
You can define a class in a program, module, package, or outside of any of these.
Defining Methods Outside
class Transaction; logic [31:0] addr; logic kind; logic [63:0] data; extern function new(); extern function void display(); endclass
transmit(t); $display("after t.display(); end endprogram transmit"); Transaction t; initial begin t = new(32'h0033); $display("before transmit"); t.display(); program testgen; task transmit(Transaction t); t = new(32’h3300); t.addr = t.addr << 2; endtask