// Name: Charles Goodliffe
// Student Code: cg829

// This module was produced by only one contributor 

// last modified: 05/12/2019

// This testbench checks the functionality of the 
// ProgramCounter module functions:
/*
   *Reset
   *LoadValue
   *Offset
   *Default Incrementation
*/

module ProgramCounterTestBench();


	// These are the signals that connect to 
	// the program counter
	logic              	Clock = '0;
	logic              	Reset;
	logic        [15:0]	LoadValue;
	logic						LoadEnable;
	logic signed  [8:0]	Offset;
	logic 					OffsetEnable;
	logic signed [15:0]	CounterValue;

	
	// instantiation of the program counter
	ProgramCounter uut(
		.Clock,
		.Reset,
		.LoadValue,
		.LoadEnable,
		.Offset,
		.OffsetEnable,
		.CounterValue
	);
	

	default clocking @(posedge Clock);
	endclocking

	always  #10  Clock++;
	
	
	initial
	begin
	
		// *****INITIALISE INPTUTS*****
		
	
		
		LoadValue = '0;
		LoadEnable = 'b0;
		Offset = '0;
		OffsetEnable = 'b0;
		
		// *****START WITH COUNTERVALUE AT 0*****
		
		Reset = 1;
		
		##1;
		
		Reset = 0;
		
		// *****TESTING INCREMENT FUNCTION*****
		
		
		##2;							// 2 +ve clock edges occur so CounterValue 
										// should increment to decimal 2
		
		
		
		
		
		// *****TESTING RESET FUNCTION*****

		Reset = 1;					// set reset input and wait for clock to go high for effect to occur	
		
		
		##1;							// PC value should reset on this +ve clock edge 
		
		
		Reset = 0;					// disable reset 
		
		
		
		
		// *****TESTING LOAD FUNCTION*****
		
		##3;							// allow 2 clk cycles to pass, PC value should be decimal 3 after 3rd cycle
		
		LoadValue = 16'b1111;		// setting load value to decimal 15
		
		##1;							// pass 1 clk cycle, the value of PC should be decimal 4 after this cycle
										// this is to show that LoadEnable needs to be active for the Load function
										// to work
										
		LoadEnable = 1;			// enable Load function
		
		##1;							// after this clk cycle the PC value
										// should be equal to the load value of decimal 15
										
		LoadEnable = 0;			// disable load function
		
		
		
		
		// *****TESTING OFFSET FUNCTION*****
		
		##5;							// allow 5 clk cycles to pass
										// the PC value should now be decimal 20
					
		Offset = -16'd10;			// assign value of decimal -10 to th offset
		
		##1;							// allow 1 clk cycle to pass to pass
										// the PC value should now be decimal 21
										// this is to show that the offset function 
										// must be enabled in order to affect the PC value
			
		OffsetEnable = 1;			// enable offset
		
		##1;							// after 1 clk cycle the PC value should now be 
										//decimal 11 (as the offset was -10 from an original
										// value of 21)
		OffsetEnable = 0;
										
		// *****END OF TESTING*****
	
	end
	
endmodule