one-hot状态机两种编码方式综合成果的比较
本帖最后由 fpgaw 于 2010-11-19 06:41 编辑1.非index编码方式
`timescale 1ns/10ps
module test_sm(
clk,
rst_n,
state_out
);
input clk;
input rst_n;
output state_out;
wire state_out;
parameter U_DLY = 1;
parameter STATE0 = 6'b000001,
STATE1 = 6'b000010,
STATE2 = 6'b000100,
STATE3 = 6'b001000,
STATE4 = 6'b010000,
STATE5 = 6'b100000;
reg current_state;
reg next_state;
assignstate_out = current_state;
//------------------------------state machine---------------------------
always @(posedge clk or negedge rst_n)
begin
if (rst_n == 1'b0)
current_state <= STATE0;
else
current_state <= #U_DLY next_state;
end
always @(current_state)
begin
case (current_state) //synopsys parallel case
STATE0:
next_state = STATE1;
STATE1:
next_state = STATE2;
STATE2:
next_state = STATE3;
STATE3:
next_state = STATE4;
STATE4:
next_state = STATE5;
STATE5:
next_state = STATE0;
default:
next_state = STATE0;
endcase
end
endmodule
2.index编码方式
`timescale 1ns/10ps
module test_sm(
clk,
rst_n,
state_out
);
input clk;
input rst_n;
output state_out;
wire state_out;
parameter U_DLY = 1;
parameter STATE0 = 0,
STATE1 = 1,
STATE2 = 2,
STATE3 = 3,
STATE4 = 4,
STATE5 = 5;
reg current_state;
reg next_state;
assignstate_out = current_state;
//------------------------------state machine---------------------------
always @(posedge clk or negedge rst_n)
begin
if (rst_n == 1'b0)
current_state <= 6'b1;//because the coding of IDLE is 000001
else
current_state <= #U_DLY next_state;
end
always @(current_state)
begin
next_state = 6'b0;
case (1'b1) //synopsys parallel case
current_state:
next_state = 1'b1;
current_state:
next_state = 1'b1;
current_state:
next_state = 1'b1;
current_state:
next_state = 1'b1;
current_state:
next_state = 1'b1;
current_state:
next_state = 1'b1;
endcase
end
endmodule
综合工具synplify、quartus4.1，器件用cyclone EP1C4-I7，没有加任务约束。
用synplify的流程为：先在synplify下综合，再导入quartus4.1布局布线。
不用synplify的流程为：直接在quartus4.1下综合。
结果：
a.非index编码：
资源占用 频率
synplify 6个LE 320M
quartus 10个LE320M
b.index编码
资源占用 频率
synplify 6个LE 320M
quartus 7个LE 320M
注：synplify将它综合成移位寄存器了，不过在另外一个用index编码的复杂的状态机中，
它是将其综合成状态机了。synplify可以认index编码的状态机，而quartus似乎不行（通过
rtl viewer来看） 综合出来的频率相同的原因可能是这状态机较为简单，体现不出差异
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