开关级建模

Verilog 还提供对晶体管级建模的支持，尽管如今设计人员很少使用它，因为电路的复杂性要求他们转向更高级别的抽象，而不是使用开关级建模。

NMOS/PMOS

  
  
module des (input d, ctrl,
			output outn, outp);
			
  nmos (outn, d, ctrl);
  pmos (outp, d, ctrl);
endmodule		

  

  
  
module tb;
  reg d, ctrl;
  wire outn, outp;
  
  des u0 (.d(d), .ctrl(ctrl), .outn(outn), .outp(outp));
  
  initial begin
    {d, ctrl} <= 0;
    
    $monitor ("T=%0t d=%0b ctrl=%0b outn=%0b outp=%0b", $time, d, ctrl, outn, outp);
    
    #10 d <= 1;
    #10 ctrl <= 1;
    #10 ctrl <= 0;
    #10 d <= 0;
  end
endmodule

  

ncsim> run
T=0 d=0 ctrl=0 outn=z outp=0
T=10 d=1 ctrl=0 outn=z outp=1
T=20 d=1 ctrl=1 outn=1 outp=z
T=30 d=1 ctrl=0 outn=z outp=1
T=40 d=0 ctrl=0 outn=z outp=0
ncsim: *W,RNQUIE: Simulation is complete.

CMOS 开关

  
  
module des (input d, nctrl, pctrl,
			output out);
			
  cmos (out, d, nctrl, pctrl);
endmodule

  

  
  
module tb;
  reg d, nctrl, pctrl;
  wire out;
  
  des u0 (.d(d), .nctrl(nctrl), .pctrl(pctrl), .out(out));
  
  initial begin
    {d, nctrl, pctrl} <= 0;
    
    $monitor ("T=%0t d=%0b nctrl=%0b pctrl=%0b out=%0b", $time, d, nctrl, pctrl, out);
    
    #10 d <= 1;
    #10 nctrl <= 1;
    #10 pctrl <= 1;
    #10 nctrl <= 0;
    #10 pctrl <= 0;
    #10 d <= 0;
    #10;
  end
endmodule

  

ncsim> run
T=0 d=0 nctrl=0 pctrl=0 out=0
T=10 d=1 nctrl=0 pctrl=0 out=1
T=20 d=1 nctrl=1 pctrl=0 out=1
T=30 d=1 nctrl=1 pctrl=1 out=1
T=40 d=1 nctrl=0 pctrl=1 out=z
T=50 d=1 nctrl=0 pctrl=0 out=1
T=60 d=0 nctrl=0 pctrl=0 out=0
ncsim: *W,RNQUIE: Simulation is complete.

双向开关

转

  
  
module des (input io1, ctrl,
            output io2);

  tran (io1, io2);	
endmodule

  

  
  
module tb;
  reg io1, ctrl;
  wire io2;
  
  des u0 (.io1(io1), .ctrl(ctrl), .io2(io2));
  
  initial begin
    {io1, ctrl} <= 0;
    
    $monitor ("T=%0t io1=%0b ctrl=%0b io2=%0b", $time, io1, ctrl, io2);
    
    #10 io1  <= 1;
    #10 ctrl <= 1;
    #10 ctrl <= 0;
    #10 io1  <= 0;
        
  end
endmodule

  

ncsim> run
T=0 io1=0 ctrl=0 io2=0
T=10 io1=1 ctrl=0 io2=1
T=20 io1=1 ctrl=1 io2=1
T=30 io1=1 ctrl=0 io2=1
T=40 io1=0 ctrl=0 io2=0
ncsim: *W,RNQUIE: Simulation is complete.

tranif0

  
  
module des (input io1, ctrl,
            output io2);
            
  tranif0 (io1, io2, ctrl);
endmodule

  

ncsim> run
T=0 io1=0 ctrl=0 io2=0
T=10 io1=1 ctrl=0 io2=1
T=20 io1=1 ctrl=1 io2=z
T=30 io1=1 ctrl=0 io2=1
T=40 io1=0 ctrl=0 io2=0
ncsim: *W,RNQUIE: Simulation is complete.

tranif1

  
  
module des (input io1, ctrl,
            output io2);
            
  tranif1 (io1, io2, ctrl);
endmodule

  

ncsim> run
T=0 io1=0 ctrl=0 io2=z
T=10 io1=1 ctrl=0 io2=z
T=20 io1=1 ctrl=1 io2=1
T=30 io1=1 ctrl=0 io2=z
T=40 io1=0 ctrl=0 io2=z
ncsim: *W,RNQUIE: Simulation is complete.

电源和接地

  
  
module des (output vdd, 
			output gnd);
			
	supply1 _vdd;
	supply0 _gnd;
	
	assign vdd = _vdd;
	assign gnd = _gnd;
endmodule						

  

  
  
module tb;
  wire vdd, gnd;
  
  des u0 (.vdd(vdd), .gnd(gnd));
  
  initial begin
    #10;
    $display ("T=%0t vdd=%0d gnd=%0d", $time, vdd, gnd);
  end
endmodule

  

ncsim> run
T=10 vdd=1 gnd=0
ncsim: *W,RNQUIE: Simulation is complete.