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1、Use verilog hdl to implement a flip-flop with synchronous RESET and SET, a Flip-flop with asynchronous RESET and SET. always@(posedge clk or negedge reset or posedge set) begin if(set) Q<> else if(!reset) Q<> else Q<> end | always@(posedge clk) begin if(set) Q<> else if(!reset) Q<> else Q<> end | 異步reset和set | 同步reset和set |
2、Use verilog hdl to implement a latch with asynchronous RESET and SET. always @(clk or reset or set) begin if(set) Q=1; else if(!reset) Q=0; else Q=D; end |
3、Use Verilog hdl to implement a 2-to-1multiplexer. assign Y=(SEL==1'b0)?A:B; |
4、Use AND gate, OR gate and Inverter toimplement a 2-to-1 multiplexer. module MUX21(A, B, SEL, Y); input A,B,SEL; output Y; net SEL_NOT, A_AND, B_AND; not u0(SEL_NOT, SEL); and u1(A_AND, SEL_NOT, A); and u2(B_AND, SEL, B); or u3(Y, A_AND, B_AND); endmodule |
5、Use a 2-to-1 multiplexer to implement a two input OR gate. module or2(A, B, Y); input A, B; output Y; MUX21 u0(Y, A, B, B ); endmodule module MUX21(Y, A ,B, SEL) input A,B,SEL; output Y; assign Y=(SEL==1’b0):A:B; endmodule | assign Y=A?A:B; |
6、Use a tri-state buffer to implement Open-Drain buffer.
7、To divide one input clock by3, Written by verilog hdl. module clk_div_3(clk, reset, clk_out); input reset,clk; output clk_out; reg clk_out; reg [1:0] cnt; always@(posedge clk or negedge reset) begin if(!reset) begin cnt<> clk_out<> else if(cnt==2'b01) begin clk_out<> cnt<=cnt+1'b1;> else if(cnt==2'b10) begin clk_out<> cnt<> else cnt<> end endmodule | 
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8、To divide one input clock by3, 50% dutycycle is required. Written by verilog hdl. module clk_div_3(clk, reset, clk_out); input reset,clk; output clk_out; reg clk_out1, clk_out2; reg [1:0] cnt1,cnt2; assign clk_out = clk_out1 | clk_out2; always@(posedge clk or negedge reset) begin if(!reset) begin cnt1<> clk_out1<> else if(cnt1==2'b01) begin clk_out1<> cnt1<=cnt1+1'b1;> else if(cnt1==2'b10) begin clk_out1<> cnt1<> else cnt1<> end always@(negedge clk or negedge reset) begin if(!reset) begin cnt2<> clk_out2<> else if(cnt2==2'b01) begin clk_out2<> cnt2<=cnt2+1'b1;> else if(cnt2==2'b10) begin clk_out2<> cnt2<> else cnt2<> end endmodule | 
| module clk_div_3(clk, reset, clk_out); input reset,clk; output clk_out; reg [1:0] cnt; reg clk_out1, clk_out2; always@(posedge clk) begin if(!reset) cnt<> else if(cnt=='d2) cnt<> else cnt<> end always @(posedge clk or negedge reset) begin if(!reset) clk_out1<> else if(cnt=='d2) clk_out1<> else if(cnt == 'd1) clk_out1<> end always @(negedge clk or negedge reset) begin if(!reset) clk_out2<> else if(cnt=='d2) clk_out2<> else if(cnt == 'd1) clk_out2<> end assign clk_out = clk_out1 | clk_out2; endmodule | 
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