T FLIP FLOP

The T Flip Flop is a complementing flip flop and can be obtained from a JK FLIP FLOP when J and K inputs are tied together. When T=0, a clock edge does not change the output; the output follows its previous output. However when T=1, the output will be the complement of its previous output. T flip flop is mostly used in design of binary and BCD counters as we will see in the upcoming blogs.

T1.jpg

Therefore, as seen from the characteristic table, when T=0, output is equal to the previous output. When T=1, the current output is the complement of previous output.

The T flip flop is constructed using D flip flop and an exclusive OR  gate through the equation.

   D = T xor Q = T Q’ + T’ Q

VERILOG CODE:

module t(clk,t,res,q);

input clk,t,res;

output reg q;

always @(posedge clk)

if(!res)

q <=1'b0;    //for initial conditions

else

case(t)

1'b0 : q <= q;

1'b1 : q <= !q;

endcase

endmodule

 

RTL SCHEMATIC:

t2.png

 

TESTBENCH:

initial begin

                                //clock signal

                                clk = 1'b1;

                                forever #10

                                clk=~clk;

                                end

                               // input signal

                                initial

                                begin

                                t=0;

                                #55;

                                t=1;

                                #20;

                               

      end

                               
                                // res signal
                                initial

                                begin

                                res=0;

                                #5;

                                res=1;

                                end

                                endmodule

 

OUTPUT:

t1.png

So can you infer something from the output ? If not here is the most important thing about T flip flop which is why it is used with microcontrollers and microprocessors. If T=1, the output frequency is exactly the half of the clock frequency. This property is used with microcontrollers and other peripherals. Various peripherals such as ADC, DAC have a clock which is very slow as compared to the microcontroller. So in order to make the clock equal, it is passed through T flip flops in order to reduce the frequency of the microcontroller.

 

 

 

 

 

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