题解 | #移位运算与乘法#
移位运算与乘法
http://www.nowcoder.com/practice/1dd22852bcac42ce8f781737f84a3272
可以用状态机实现，代码如下：
`timescale 1ns/1ns
module multi_sel(
input [7:0]d ,
input clk,
input rst,
output reg input_grant,
output reg [10:0]out
);
reg[1:0] state;
reg[7:0] d1;
always@ (posedge clk or negedge rst) begin
if(~rst) begin
input_grant <= 0; out <= 0; state <= 0; d1 <= 0;
end
else begin
if (input_grant == 1)
input_grant <= 0;
else input_grant <= input_grant;
case(state)
0://d乘1,用d1将d的值锁存进去
begin
out <= d;
d1 <= d;
input_grant <= 1;
state <= 1;
end
1://d乘3
begin
out <= d1 + {d1,1'b0};
state <= 2;
end
2://d乘7
begin
out <= d1 + {d1,1'b0} + {d1,2'b00};
state <= 3;
end
3://d乘8
begin
out <= {d1,3'b000};
state <= 0;
end
endcase
end
end
endmodule
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