src_xtn.sv

class write_xtn extends uvm_sequence_item;

	`uvm_object_utils(write_xtn)

	rand bit[7:0] header;//[1:0] address
	rand bit[7:0] payload_data[];//header will decide the payload length from [7:2]

	bit[7:0]parity;//xor operation of header with payloads
	bit err;

	constraint c1{header[1:0]!=3;}//no address for 11
	constraint c2{payload_data.size == header[7:2];}//payload size decided by header [7:2]
	constraint c3{payload_data.size!=0;}//payload size should not be zero

	extern function new(string name = "write_xtn");
	extern function void post_randomize();
	extern function void do_print(uvm_printer printer);

endclass



function write_xtn::new(string name = "write_xtn");
        super.new(name);
endfunction : new



function void write_xtn::post_randomize();//after randomization, to calculate the parity
	parity = 0 ^ header;
	foreach(payload_data[i])
		parity = parity ^ payload_data[i];
endfunction



function void  write_xtn::do_print (uvm_printer printer);
        super.do_print(printer);

	//                  srting name             bitstream value     size    radix for printing
    	printer.print_field( "header",                        this.header,              8,              UVM_HEX                );

	foreach(payload_data[i])
    		printer.print_field($sformatf("payload_data[%0d]",i),             this.payload_data[i],       8,          UVM_HEX                );
    	printer.print_field( "parity",                       this.parity,         8,                UVM_HEX               );

endfunction:do_print