dual_sim.v

各种基本单元的verilog模块.对初学者很有帮助的.

/*********************************************************/
// MODULE:		Dual Port RAM simulation
//
// FILE NAME:	dual_sim.v
// VERSION:		1.0
// DATE:		January 1, 1999
// AUTHOR:		Bob Zeidman, Zeidman Consulting
// 
// CODE TYPE:	Simulation
//
// DESCRIPTION:	This module provides stimuli for simulating
// a Dual Port Random Access Memory. It writes unique values
// to each location then reads them back and checks for
// correctness. Read back of the RAM begins before writing
// has finished to check that both can occur simultaneously.
//
/*********************************************************/

// DEFINES
`define DEL	1			// Clock-to-output delay. Zero
						// time delays can be confusing
						// and sometimes cause problems.

`define RAM_WIDTH 8		// Width of RAM (number of bits)
`define RAM_DEPTH 16	// Depth of RAM (number of bytes)
`define ADDR_SZ 4		// Number of bits required to
						// represent the RAM address

// TOP MODULE
module dual_sim();

// INPUTS

// OUTPUTS

// INOUTS

// SIGNAL DECLARATIONS
reg						clk;
reg  [`ADDR_SZ-1:0] 	rd_address;
reg  [`ADDR_SZ-1:0] 	wr_address;
reg 					read;
reg 					write;
reg  [`RAM_WIDTH-1:0]	data_in;
wire [`RAM_WIDTH-1:0]	data_out;

reg  [`RAM_WIDTH-1:0]	data_exp;	// Expected output data
integer					cyc_count;	// Cycle counter

// PARAMETERS

// ASSIGN STATEMENTS

// MAIN CODE

// Instantiate the counter
Dual dual(
		.clk(clk),
		.data_in(data_in),
		.rd_address(rd_address),
		.read(read),
		.data_out(data_out),
		.wr_address(wr_address),
		.write(write));

// Initialize inputs
initial begin
	data_in = 0;
	data_exp = 0;
	rd_address = 0;
	wr_address = 0;
	clk = 1;
	cyc_count = 0;
	write = 1;			// Start writing
	read = 0;			// Start reading later
end

// Generate the clock
always #100 clk = ~clk;

// Simulate
// Write the RAM
always @(posedge clk) begin
	// Give a delay for outputs to settle
	#`DEL;
	#`DEL;

	if (write) begin
		// Set up the write address for the next write
		wr_address = wr_address + 1;
		if (wr_address === 0) begin
			// If the address is 0, we've written the entire RAM
			// Deassert the write control
			write = 0;
		end
		else begin
			// Otherwise set up the data for the next write
			// We decrement data while incrementing address
			// so that we know we are writing the data, not 
			// the address into memory
			data_in = data_in - 1;
		end
	end

	if (read) begin
		// Read the data and compare
		if (data_out !== data_exp) begin
			$display("\nERROR at time %0t:", $time);
			$display("    Data read     = %h", data_out);
			$display("    Data expected = %h\n", data_exp);
					
			// Use $stop for debugging
			$stop;
		end
		
		// Increment the read address
		rd_address = rd_address + 1;
		if (rd_address === 0) begin
			// If the address is 0, we've read the entire RAM
			$display("\nSimulation complete - no errors\n");
			$finish;
		end

		// Decrement the expected data
		data_exp <= data_exp - 1;
	end

	// Increment the cycle counter
	cyc_count = cyc_count + 1;

	// Start reading at some point
	if (cyc_count == (`RAM_DEPTH/2 + 2)) begin
	   	// Assert the read control
	   	read = 1;
	end
end
endmodule		// dual_sim