FPGA的數(shù)字信號處理：Verilog實現(xiàn)簡單的FIR濾波器

該項目介紹了如何使用 Verilog 實現(xiàn)具有預(yù)生成系數(shù)的簡單 FIR 濾波器。

緒論

不起眼的 FIR 濾波器是 FPGA 數(shù)字信號處理中最基本的模塊之一，因此了解如何將具有給定抽頭數(shù)及其相應(yīng)系數(shù)值的基本模塊組合在一起非常重要。因此，在這個關(guān)于 FPGA 上 DSP 基礎(chǔ)實用入門的教程中，將從一個簡單的 15 抽頭低通濾波器 FIR 開始，在 Matlab 中為其生成初始系數(shù)值，然后轉(zhuǎn)換這些值用于編寫 Verilog 模塊。

有限脈沖響應(yīng)或 FIR 濾波器定義為脈沖響應(yīng)在特定時間段內(nèi)穩(wěn)定為零值的濾波器。脈沖響應(yīng)穩(wěn)定到零所花費的時間與濾波器階數(shù)（抽頭數(shù)）直接相關(guān)，濾波器階數(shù)是 FIR 的基礎(chǔ)傳遞函數(shù)多項式的階數(shù)。FIR 的傳遞函數(shù)不包含反饋，因此如果輸入一個值為 1 的脈沖，然后輸入一串零值，輸出將只是濾波器的系數(shù)值。

濾波器的作用基本都是用于信號調(diào)節(jié)，主要集中在選擇濾除或允許通過哪些頻率。最簡單的例子之一是低通濾波器，它允許低于某個閾值（截止頻率）的頻率通過，同時大大衰減高于該閾值的頻率，如下圖所示。

該項目的主要重點是在 HDL（具體為 Verilog）中實現(xiàn) FIR，它可以分解為三個主要邏輯組件：一個循環(huán)緩沖器，用于將每個樣本計時到適當(dāng)?shù)乜紤]了串行輸入的延遲、每個抽頭系數(shù)值的乘法器以及每個抽頭輸出的求和結(jié)果的累加器。

由于本項目專注于 FPGA 邏輯中 FIR 的設(shè)計機制，所以只是使用 Simulink 中的 FDA 工具和 Matlab 為低通濾波器插入一些簡單參數(shù)，然后使用生成的系數(shù)值放到 Verilog 模塊中完成濾波器的設(shè)計（在后面的步驟中完成）。

選擇實現(xiàn)一個簡單的 15 抽頭低通濾波器 FIR，采樣率為 1Ms/s，通帶頻率為 200kHz，阻帶頻率為 355kHz，得到以下系數(shù)：

-0.0265
0
0.0441
0
-0.0934
0
0.3139
0.5000
0.3139
0
-0.0934
0
0.0441
0
-0.0265

為 FIR 模塊創(chuàng)建設(shè)計文件

在 Vivado 項目中添加源文件。

在確定 FIR 的順序（抽頭數(shù)）并獲得系數(shù)值后，接下來需要定義的下一組參數(shù)就是輸入樣本、輸出樣本和系數(shù)本身的位寬。

對于這個 FIR，選擇將輸入樣本和系數(shù)寄存器設(shè)置為 16 位寬，并將輸出樣本寄存器設(shè)置為 32 位，因為兩個 16 位值的乘積是一個 32 位值（兩個值的寬度相乘得到乘積的寬度，所以如果選擇了 8 位抽頭的 16 位輸入樣本，那么輸出樣本將為 24 位寬）。

這些值也都是帶符號的，因此 MSB 用作符號位，在選擇輸入樣本寄存器的初始寬度時一定要記住這一點。要在 Verilog 中將這些值設(shè)置為有符號數(shù)據(jù)類型，使用關(guān)鍵字signed ：

regsigned[15:0]register_name;

接下來要解決的是如何在 Verilog 中處理系數(shù)值，小數(shù)點值需要轉(zhuǎn)換為定點值。由于所有系數(shù)值都小于 1，因此寄存器的所有 15 位（總共 16 位，MSB 是有符號位）都可以用于小數(shù)位。通常，必須決定要將寄存器中的多少位用于數(shù)字的整數(shù)部分與數(shù)字的小數(shù)部分。因此，轉(zhuǎn)換分數(shù)值抽頭的數(shù)學(xué)是：(fractional coefficient value)*(2^(15))該乘積的小數(shù)值被四舍五入，并且如果系數(shù)為負，則計算該值的二進制補碼：

tap0=twos(-0.0265*32768)=0xFC9C
tap1=0
tap2=0.0441*32768=1445.0688=1445=0x05A5
tap3=0
tap4=twos(-0.0934*32768)=0xF40C
tap5=0
tap6=0.3139*32768=10285.8752=10285=0x282D
tap7=0.5000*32768=16384=0x4000
tap8=0.3139*32768=10285.8752=10285=0x282D
tap9=0
tap10=twos(-0.0934*32768)=0xF40C
tap11=0
tap12=0.0441*32768=1445.0688=1445=0x05A5
tap13=0
tap14=twos(-0.0265*32768)=0xFC9C

現(xiàn)在我們終于準(zhǔn)備好關(guān)注 FIR 模塊的邏輯，第一個是循環(huán)緩沖區(qū)，它引入串行輸入樣本流并為濾波器的 15 個抽頭創(chuàng)建一個包含 15 個輸入樣本的數(shù)組。

always@(posedgeclk)
begin
if(enable_buff==1'b1)
begin
buff0<=?in_sample;
????????????????????buff1?<=?buff0;????????
????????????????????buff2?<=?buff1;?????????
????????????????????buff3?<=?buff2;??????
????????????????????buff4?<=?buff3;??????
????????????????????buff5?<=?buff4;???????
????????????????????buff6?<=?buff5;????
????????????????????buff7?<=?buff6;???????
????????????????????buff8?<=?buff7;???????
????????????????????buff9?<=?buff8;???????
????????????????????buff10?<=?buff9;????????
????????????????????buff11?<=?buff10;???????
????????????????????buff12?<=?buff11;???????
????????????????????buff13?<=?buff12;???????
????????????????????buff14?<=?buff13;????
????????????????end
????????end

接下來，乘法階段將每個樣本乘以每個系數(shù)值：

/*MultiplystageofFIR*/
always@(posedgeclk)
begin
if(enable_fir==1'b1)
begin
acc0<=?tap0?*?buff0;
????????????????????acc1?<=?tap1?*?buff1;
????????????????????acc2?<=?tap2?*?buff2;
????????????????????acc3?<=?tap3?*?buff3;
????????????????????acc4?<=?tap4?*?buff4;
????????????????????acc5?<=?tap5?*?buff5;
????????????????????acc6?<=?tap6?*?buff6;
????????????????????acc7?<=?tap7?*?buff7;
????????????????????acc8?<=?tap8?*?buff8;
????????????????????acc9?<=?tap9?*?buff9;
????????????????????acc10?<=?tap10?*?buff10;
????????????????????acc11?<=?tap11?*?buff11;
????????????????????acc12?<=?tap12?*?buff12;
????????????????????acc13?<=?tap13?*?buff13;
????????????????????acc14?<=?tap14?*?buff14;
????????????????end
????????end

乘法階段的結(jié)果值通過加法累加到寄存器中，最終成為濾波器的輸出數(shù)據(jù)流。

/*AccumulatestageofFIR*/
always@(posedgeclk)
begin
if(enable_fir==1'b1)
begin
m_axis_fir_tdata<=?acc0?+?acc1?+?acc2?+?acc3?+?acc4?+?acc5?+?acc6?+?acc7?+?acc8?+?acc9?+?acc10?+?acc11?+?acc12?+?acc13?+?acc14;
????????????????end
????????end

最后，邏輯的最后一部分是將數(shù)據(jù)流進和流出 FIR 模塊的接口。AXI Stream 接口是最常見的接口之一。關(guān)鍵方面是允許控制上游和下游設(shè)備之間的數(shù)據(jù)流的tready和tvalid信號。這意味著 FIR 模塊需要向其下游設(shè)備提供tvalid信號以指示其輸出是有效數(shù)據(jù)，并且如果下游設(shè)備解除其tready信號，則能夠暫停（但仍保留）其輸出。FIR 模塊還必須能夠與其主端接口上的上游設(shè)備以同樣的方式運行。

以下是 FIR 模塊的邏輯設(shè)計概述：

請注意tready和tvalid信號如何設(shè)置輸入循環(huán)緩沖器的使能值和 FIR 的乘法級以及數(shù)據(jù)或系數(shù)通過的每個寄存器都被聲明為有符號的。

FIR模塊Verilog代碼：

`timescale1ns/1ps

moduleFIR(
inputclk,
inputreset,
inputsigned[15:0]s_axis_fir_tdata,
input[3:0]s_axis_fir_tkeep,
inputs_axis_fir_tlast,
inputs_axis_fir_tvalid,
inputm_axis_fir_tready,
outputregm_axis_fir_tvalid,
outputregs_axis_fir_tready,
outputregm_axis_fir_tlast,
outputreg[3:0]m_axis_fir_tkeep,
outputregsigned[31:0]m_axis_fir_tdata
);


always@(posedgeclk)
begin
m_axis_fir_tkeep<=?4'hf;
????????end
????????
????always?@?(posedge?clk)
????????begin
????????????if?(s_axis_fir_tlast?==?1'b1)
????????????????begin
????????????????????m_axis_fir_tlast?<=?1'b1;
????????????????end
????????????else
????????????????begin
????????????????????m_axis_fir_tlast?<=?1'b0;
????????????????end
????????end
????
????//?15-tap?FIR?
????reg?enable_fir,?enable_buff;
????reg?[3:0]?buff_cnt;
????reg?signed?[15:0]?in_sample;?
????reg?signed?[15:0]?buff0,?buff1,?buff2,?buff3,?buff4,?buff5,?buff6,?buff7,?buff8,?buff9,?buff10,?buff11,?buff12,?buff13,?buff14;?
????wire?signed?[15:0]?tap0,?tap1,?tap2,?tap3,?tap4,?tap5,?tap6,?tap7,?tap8,?tap9,?tap10,?tap11,?tap12,?tap13,?tap14;?
????reg?signed?[31:0]?acc0,?acc1,?acc2,?acc3,?acc4,?acc5,?acc6,?acc7,?acc8,?acc9,?acc10,?acc11,?acc12,?acc13,?acc14;?

????
????/*?Taps?for?LPF?running?@?1MSps?with?a?cutoff?freq?of?400kHz*/
????assign?tap0?=?16'hFC9C;??//?twos(-0.0265?*?32768)?=?0xFC9C
????assign?tap1?=?16'h0000;??//?0
????assign?tap2?=?16'h05A5;??//?0.0441?*?32768?=?1445.0688?=?1445?=?0x05A5
????assign?tap3?=?16'h0000;??//?0
????assign?tap4?=?16'hF40C;??//?twos(-0.0934?*?32768)?=?0xF40C
????assign?tap5?=?16'h0000;??//?0
????assign?tap6?=?16'h282D;??//?0.3139?*?32768?=?10285.8752?=?10285?=?0x282D
????assign?tap7?=?16'h4000;??//?0.5000?*?32768?=?16384?=?0x4000
????assign?tap8?=?16'h282D;??//?0.3139?*?32768?=?10285.8752?=?10285?=?0x282D
????assign?tap9?=?16'h0000;??//?0
????assign?tap10?=?16'hF40C;?//?twos(-0.0934?*?32768)?=?0xF40C
????assign?tap11?=?16'h0000;?//?0
????assign?tap12?=?16'h05A5;?//?0.0441?*?32768?=?1445.0688?=?1445?=?0x05A5
????assign?tap13?=?16'h0000;?//?0
????assign?tap14?=?16'hFC9C;?//?twos(-0.0265?*?32768)?=?0xFC9C
????
????/*?This?loop?sets?the?tvalid?flag?on?the?output?of?the?FIR?high?once?
?????*?the?circular?buffer?has?been?filled?with?input?samples?for?the?
?????*?first?time?after?a?reset?condition.?*/
????always?@?(posedge?clk?or?negedge?reset)
????????begin
????????????if?(reset?==?1'b0)?//if?(reset?==?1'b0?||?tvalid_in?==?1'b0)
????????????????begin
????????????????????buff_cnt?<=?4'd0;
????????????????????enable_fir?<=?1'b0;
????????????????????in_sample?<=?8'd0;
????????????????end
????????????else?if?(m_axis_fir_tready?==?1'b0?||?s_axis_fir_tvalid?==?1'b0)
????????????????begin
????????????????????enable_fir?<=?1'b0;
????????????????????buff_cnt?<=?4'd15;
????????????????????in_sample?<=?in_sample;
????????????????end
????????????else?if?(buff_cnt?==?4'd15)
????????????????begin
????????????????????buff_cnt?<=?4'd0;
????????????????????enable_fir?<=?1'b1;
????????????????????in_sample?<=?s_axis_fir_tdata;
????????????????end
????????????else
????????????????begin
????????????????????buff_cnt?<=?buff_cnt?+?1;
????????????????????in_sample?<=?s_axis_fir_tdata;
????????????????end
????????end???

????always?@?(posedge?clk)
????????begin
????????????if(reset?==?1'b0?||?m_axis_fir_tready?==?1'b0?||?s_axis_fir_tvalid?==?1'b0)
????????????????begin
????????????????????s_axis_fir_tready?<=?1'b0;
????????????????????m_axis_fir_tvalid?<=?1'b0;
????????????????????enable_buff?<=?1'b0;
????????????????end
????????????else
????????????????begin
????????????????????s_axis_fir_tready?<=?1'b1;
????????????????????m_axis_fir_tvalid?<=?1'b1;
????????????????????enable_buff?<=?1'b1;
????????????????end
????????end
????
????/*?Circular?buffer?bring?in?a?serial?input?sample?stream?that?
?????*?creates?an?array?of?15?input?samples?for?the?15?taps?of?the?filter.?*/
????always?@?(posedge?clk)
????????begin
????????????if(enable_buff?==?1'b1)
????????????????begin
????????????????????buff0?<=?in_sample;
????????????????????buff1?<=?buff0;????????
????????????????????buff2?<=?buff1;?????????
????????????????????buff3?<=?buff2;??????
????????????????????buff4?<=?buff3;??????
????????????????????buff5?<=?buff4;???????
????????????????????buff6?<=?buff5;????
????????????????????buff7?<=?buff6;???????
????????????????????buff8?<=?buff7;???????
????????????????????buff9?<=?buff8;???????
????????????????????buff10?<=?buff9;????????
????????????????????buff11?<=?buff10;???????
????????????????????buff12?<=?buff11;???????
????????????????????buff13?<=?buff12;???????
????????????????????buff14?<=?buff13;????
????????????????end
????????????else
????????????????begin
????????????????????buff0?<=?buff0;
????????????????????buff1?<=?buff1;????????
????????????????????buff2?<=?buff2;?????????
????????????????????buff3?<=?buff3;??????
????????????????????buff4?<=?buff4;??????
????????????????????buff5?<=?buff5;???????
????????????????????buff6?<=?buff6;????
????????????????????buff7?<=?buff7;???????
????????????????????buff8?<=?buff8;???????
????????????????????buff9?<=?buff9;???????
????????????????????buff10?<=?buff10;????????
????????????????????buff11?<=?buff11;???????
????????????????????buff12?<=?buff12;???????
????????????????????buff13?<=?buff13;???????
????????????????????buff14?<=?buff14;
????????????????end
????????end
????????
????/*?Multiply?stage?of?FIR?*/
????always?@?(posedge?clk)
????????begin
????????????if?(enable_fir?==?1'b1)
????????????????begin
????????????????????acc0?<=?tap0?*?buff0;
????????????????????acc1?<=?tap1?*?buff1;
????????????????????acc2?<=?tap2?*?buff2;
????????????????????acc3?<=?tap3?*?buff3;
????????????????????acc4?<=?tap4?*?buff4;
????????????????????acc5?<=?tap5?*?buff5;
????????????????????acc6?<=?tap6?*?buff6;
????????????????????acc7?<=?tap7?*?buff7;
????????????????????acc8?<=?tap8?*?buff8;
????????????????????acc9?<=?tap9?*?buff9;
????????????????????acc10?<=?tap10?*?buff10;
????????????????????acc11?<=?tap11?*?buff11;
????????????????????acc12?<=?tap12?*?buff12;
????????????????????acc13?<=?tap13?*?buff13;
????????????????????acc14?<=?tap14?*?buff14;
????????????????end
????????end????
????????
?????/*?Accumulate?stage?of?FIR?*/???
????always?@?(posedge?clk)?
????????begin
????????????if?(enable_fir?==?1'b1)
????????????????begin
????????????????????m_axis_fir_tdata?<=?acc0?+?acc1?+?acc2?+?acc3?+?acc4?+?acc5?+?acc6?+?acc7?+?acc8?+?acc9?+?acc10?+?acc11?+?acc12?+?acc13?+?acc14;
????????????????end
????????end?????

????
????
endmodule

創(chuàng)建仿真文件

要測試 FIR 模塊，需要創(chuàng)建一個測試平臺作為其仿真源：

在 FIR 模塊中有兩個主要的東西需要測試：濾波器算法和 AXI 流接口。為實現(xiàn)這一點，測試臺中創(chuàng)建了一個狀態(tài)機，它生成一個簡單的 200kHz 正弦波，并切換從屬端的有效信號和 FIR 接口主控端的tready信號。

FIR 模塊的測試平臺：

`timescale1ns/1ps

moduletb_FIR;

regclk,reset,s_axis_fir_tvalid,m_axis_fir_tready;
regsigned[15:0]s_axis_fir_tdata;
wirem_axis_fir_tvalid;
wire[3:0]m_axis_fir_tkeep;
wire[31:0]m_axis_fir_tdata;

/*
*100Mhz(10ns)clock
*/
alwaysbegin
clk=1;#5;
clk=0;#5;
end

alwaysbegin
reset=1;#20;
reset=0;#50;
reset=1;#1000000;
end

alwaysbegin
s_axis_fir_tvalid=0;#100;
s_axis_fir_tvalid=1;#1000;
s_axis_fir_tvalid=0;#50;
s_axis_fir_tvalid=1;#998920;
end

alwaysbegin
m_axis_fir_tready=1;#1500;
m_axis_fir_tready=0;#100;
m_axis_fir_tready=1;#998400;
end

/*InstantiateFIRmoduletotest.*/
FIRFIR_i(
.clk(clk),
.reset(reset),
.s_axis_fir_tdata(s_axis_fir_tdata),
.s_axis_fir_tkeep(s_axis_fir_tkeep),
.s_axis_fir_tlast(s_axis_fir_tlast),
.s_axis_fir_tvalid(s_axis_fir_tvalid),
.m_axis_fir_tready(m_axis_fir_tready),
.m_axis_fir_tvalid(m_axis_fir_tvalid),
.s_axis_fir_tready(s_axis_fir_tready),
.m_axis_fir_tlast(m_axis_fir_tlast),
.m_axis_fir_tkeep(m_axis_fir_tkeep),
.m_axis_fir_tdata(m_axis_fir_tdata));

reg[4:0]state_reg;
reg[3:0]cntr;

parameterwvfm_period=4'd4;

parameterinit=5'd0;
parametersendSample0=5'd1;
parametersendSample1=5'd2;
parametersendSample2=5'd3;
parametersendSample3=5'd4;
parametersendSample4=5'd5;
parametersendSample5=5'd6;
parametersendSample6=5'd7;
parametersendSample7=5'd8;

/*Thisstatemachinegeneratesa200kHzsinusoid.*/
always@(posedgeclkorposedgereset)
begin
if(reset==1'b0)
begin
cntr<=?4'd0;
????????????????????s_axis_fir_tdata?<=?16'd0;
????????????????????state_reg?<=?init;
????????????????end
????????????else
????????????????begin
????????????????????case?(state_reg)
????????????????????????init?:?//0
????????????????????????????begin
????????????????????????????????cntr?<=?4'd0;
????????????????????????????????s_axis_fir_tdata?<=?16'h0000;
????????????????????????????????state_reg?<=?sendSample0;
????????????????????????????end
????????????????????????????
????????????????????????sendSample0?:?//1
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h0000;
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample1;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample0;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample1?:?//2
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h5A7E;?
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample2;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample1;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample2?:?//3
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h7FFF;
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample3;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample2;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample3?:?//4
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h5A7E;
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample4;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample3;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample4?:?//5
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h0000;
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample5;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample4;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample5?:?//6
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'hA582;?
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample6;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample5;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample6?:?//6
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'h8000;?
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample7;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample6;
????????????????????????????????????end
????????????????????????????end?
????????????????????????
????????????????????????sendSample7?:?//6
????????????????????????????begin
????????????????????????????????s_axis_fir_tdata?<=?16'hA582;?
????????????????????????????????
????????????????????????????????if?(cntr?==?wvfm_period)
????????????????????????????????????begin
????????????????????????????????????????cntr?<=?4'd0;
????????????????????????????????????????state_reg?<=?sendSample0;
????????????????????????????????????end
????????????????????????????????else
????????????????????????????????????begin?
????????????????????????????????????????cntr?<=?cntr?+?1;
????????????????????????????????????????state_reg?<=?sendSample7;
????????????????????????????????????end
????????????????????????????end?????????????????????
????????????????????
????????????????????endcase
????????????????end
????????end
????
endmodule

運行行為仿真

FIR 模塊及其測試平臺文件就位后，從 Flow Navigator 窗口啟動 Vivado 中的仿真器，選擇 Run Behavioral Simulation 選項。

如行為仿真所示，F(xiàn)IR 正確過濾信號并正確響應(yīng) AXI 流信號。

總結(jié)

代碼都在上面大家有興趣可以自行運行，但是大家可能會注意到，這個 FIR 模塊在設(shè)計上運行綜合和實現(xiàn)時時序應(yīng)該是不能通過的。我們將在下一篇文章中詳細介紹如何在無法滿足時序要求時重新設(shè)計你的設(shè)計~

審核編輯：湯梓紅