Implementation of Verilog Code for Reading and Writing Registers of LocalBUS Bus (2)-Writing of Testbench for Inout Bidirectional Bus

Testbench considerations

In this example, the difficulty of testbench lies in how to simulate the two-way signal. By searching for information, I found the following method to realize the simulation of inout-type signals.

reg [7:0]BMD$inout$reg;
wire [7:0]BMD = BMD$inout$reg;

Teshbench source code

When writing the bus, pass
BMD$inout$reg = 8'ha5;
to assign value.
When reading the bus, you only need to assign a value to the address.

`timescale 1ns/1ns
`define clock_period 20

module regs_tb;
	reg clk;
	reg rst_n;
	
	reg [7:0]BMA;

	reg nBOE;
	reg nBWE;
	reg nBCS1;

	reg [7:0]BMD$inout$reg = 8'b0000_0000;
	wire [7:0]BMD = BMD$inout$reg;

	wire HDDog_close;  //8'h60,	F500_180  ADDR[9:2] write 5a
//	wire SFTDog_close; //8'h71,   F500_01C4 read close soft dog
//	wire SFTDog_open;  //8'h71,   F500_01C4 write a5 open soft dog
	wire SFTDog_en;
	wire SFTDog_clr;	 //8'h72,   F500_01C8 write aa
	
	wire SFTDog_close_view; //8'h71,   F500_01C4 read close soft dog
	wire SFTDog_open_view;  //8'h71,   F500_01C4 write a5 open soft dog
	

assign 	SFTDog_close_view = regs0.SFTDog_close;
assign 	SFTDog_open_view = regs0.SFTDog_open;
	
	regs	regs0(
			.Clk(clk),
			.Rst_n(rst_n),
			.BMA(BMA),
			.BMD(BMD),
			.nBOE(nBOE),
			.nBWE(nBWE),
			.nBCS1(nBCS1),
			.HDDog_close(HDDog_close),
			.SFTDog_en(SFTDog_en),
			.SFTDog_clr(SFTDog_clr)
	);
	
	initial clk = 1;
	always #(`clock_period/2) clk = ~clk;
	
	initial begin
		rst_n = 1'b0;
		#(`clock_period *100);
		rst_n = 1'b1;
		#(`clock_period *100);
		
		nBCS1 = 1;
		nBOE = 1;
		nBWE = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *100);
		
	//read
		BMA = 8'h61;
		nBCS1 = 0;
		#(`clock_period *2);	
		nBOE = 0;
		nBWE = 1;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		#(`clock_period *10);
		
    //write
		BMA = 8'h61;
		BMD$inout$reg = 8'ha5;
		nBCS1 = 0;
		#(`clock_period *2);		
		nBOE = 1;
		nBWE = 0;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *10);
		
	//read
		BMA = 8'h61;
		nBCS1 = 0;
		#(`clock_period *2);	
		nBOE = 0;
		nBWE = 1;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		#(`clock_period *10);
		
	 //write  HDDog_close
		BMA = 8'h60;
		BMD$inout$reg = 8'h5a;
		nBCS1 = 0;
		#(`clock_period *2);		
		nBOE = 1;
		nBWE = 0;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *10);
		

	//read SFTDog_close
		BMA = 8'h71;
		nBCS1 = 0;
		#(`clock_period *2);	
		nBOE = 0;
		nBWE = 1;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		#(`clock_period *10);
		
	 //write  SFTDog_open
		BMA = 8'h71;
		BMD$inout$reg = 8'ha5;
		nBCS1 = 0;
		#(`clock_period *2);		
		nBOE = 1;
		nBWE = 0;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *30);
		
			//read SFTDog_close
		BMA = 8'h71;
		nBCS1 = 0;
		#(`clock_period *2);	
		nBOE = 0;
		nBWE = 1;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		#(`clock_period *30);
		
	 //write  SFTDog_open
		BMA = 8'h71;
		BMD$inout$reg = 8'ha5;
		nBCS1 = 0;
		#(`clock_period *2);		
		nBOE = 1;
		nBWE = 0;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *30);
		
	 //write  SFTDog_clr
		BMA = 8'h72;
		BMD$inout$reg = 8'haa;
		nBCS1 = 0;
		#(`clock_period *2);		
		nBOE = 1;
		nBWE = 0;
		#(`clock_period *3);
		nBOE = 1;
		nBWE = 1;
		#(`clock_period *2);
		nBCS1 = 1;
		BMA = 8'hff;
		BMD$inout$reg = 8'hzz;
		#(`clock_period *10);
		
		$stop;
	end
	
endmodule

Simulation waveform

The default value of the register to be tested is 0x3c after power-on. Perform a write operation (write 0xa5), read the register again, and the return value is 0xa5. Successful operation.