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module dff(clk, d, q);
input clk, d;
output reg q;
always @(posedge clk)
q <= d;
endmodule
module dffa(clk, arst, d, q);
input clk, arst, d;
output reg q;
always @(posedge clk or posedge arst) begin
if (arst)
q <= 1;
else
q <= d;
end
endmodule
module dffa1(clk, arst, d, q);
input clk, arst, d;
output reg q;
always @(posedge clk or negedge arst) begin
if (~arst)
q <= 0;
else
q <= d;
end
endmodule
module dffa2(clk, arst, d, q);
input clk, arst, d;
output reg q;
always @(posedge clk or negedge arst) begin
if (!arst)
q <= 0;
else
q <= d;
end
endmodule
module dffa3(clk, arst, d, q);
input clk, arst, d;
output reg q;
always @(posedge clk or negedge arst) begin
if (~(!arst))
q <= d;
else
q <= 1;
end
endmodule
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