SPI一共4個(gè)線：*）SCK 串行時(shí)鐘線：時(shí)鐘信號
本文引用地址：http://www.biyoush.com/article/201612/329837.htm*）MISO 主機(jī)輸入/從機(jī)輸出線；
*）MOSI 主機(jī)輸出/從機(jī)輸入線；
*）CS 片選那個(gè)從機(jī)進(jìn)行通信。
無應(yīng)答機(jī)制
一定要搞清楚從設(shè)備是上升沿還是下降沿接受數(shù)據(jù)。
時(shí)鐘極性：一根線上比如：主的SDO和從的SDI時(shí)鐘極性相反，也就是如果主SDO是上升沿有效，那么從SDI下降沿有效。
時(shí)鐘相位為0：第一個(gè)跳變沿?cái)?shù)據(jù)采樣，所以時(shí)鐘前采樣，時(shí)鐘后輸出；
時(shí)鐘相位為1：第二個(gè)跳變沿?cái)?shù)據(jù)采樣，所以時(shí)鐘前輸出，時(shí)鐘后采樣。
一般使用0模式。
管腳SS非為判斷主從的標(biāo)志，SS非為低為從，高為主。
IP可劃分為：硬IP，軟IP，和兩者之間的固IP
SPI
module spi_mosi(rst,clk,rd,wr,datain,spics,spiclk,spido,spidi,dataout);
input rst;//置位信號，低有效
input clk;//時(shí)鐘信號
input rd;//接受數(shù)據(jù)命令
input wr;//發(fā)送數(shù)據(jù)命令
input spidi;//SPI數(shù)據(jù)輸入信號
input [7:0] datain;//待發(fā)送數(shù)據(jù)~輸入
output spics;//SPI片選信號
ouput spiclk；//SPI時(shí)鐘信號
output spido；//SPI數(shù)據(jù)輸出信號
output [7:0] dataout;//待接受數(shù)據(jù)~輸出
reg spics;
reg spiclk;
reg spido;
reg [7:0] dstate,dsend,dataout,dreceive;
reg [1:0] spistate;
parameter idle = 2b00;
parameter send_data=2b01;
parameter receive_data=2b10;
initial
begin
spics<=1b1;
spiclk<=1b1;
spido<=1b1;
end
always @(posedge clk)
begin
if(!rst)
begin
spistate<=idle;
spics<=1b1;
spiclk<=1b1;
spido<=1b1;
dstate<=8d0;
end
else
begin
case(spistate)
2b00:
begin
if((wr==1b0)&&(rd==1b1))//發(fā)送數(shù)據(jù)轉(zhuǎn)換
begin
spistate<=send_data;
dstate<=8d0;
dsend<=datain;
end
else if((wr==1b1)&&(rd==1b0))//接受數(shù)據(jù)轉(zhuǎn)換
begin
spistate<=receive_data;
dstate<=8d0;
end
else
begin
spistate<=idle;
dstate<=8d0;
end
end
2b01://發(fā)送數(shù)據(jù)狀態(tài)
begin
case(state)
8d0://產(chǎn)生片選信號有效
begin
spics<=1b0;
spiclk<=1b1;
spicdo<=1b1;
dstate<=8d1;
8d1:
begin
spics<=1b0;
spiclk<=1b1;
spido<=1b1;
dstate<=8d2;
end
8d2:
begin
spics<=1b0;
spiclk<=1b0;
spido<=1b1;
dstate<=8d3;
end
8d3:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[7];//發(fā)送數(shù)據(jù)最高位
dstate<=8d4;
end
8’d4:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[7];
dstate<=8d5;
end
8d5:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[6];
dstate<=8d6;
end
8d6:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[6];
dstate<=8d7;
end
8d7:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[5];
dstate<=8d8;
end
8d8:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[5];
dstate<=8d9;
end
8d9:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[4];
dstate<=8d10;
end
8d10:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[4];
dstate<=8d11;
end
8d11:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[3];
dstate<=8d12;
end
8d12:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[3];
dstate<=8d13;
end
8d13:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[2];
dstate<=8d14;
end
8d14:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[2];
dstate<=8d15;
end
8d15:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[1];
dstate<=8d7;
end
8d16:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[1];
dstate<=8d17;
end
8d17:
begin
spics<=1b0;
spiclk<=1b0;
spido<=dsend[0];
dstate<=8d18;
end
8d18:
begin
spics<=1b0;
spiclk<=1b1;
spido<=dsend[0];
dstate<=8d19;
end
8d19:
begin
spics<=1b1;
spiclk<=1b1;
spido<=1b1;
dstate<=8d20;
end
8d20:
begin
spics<=1b1;
spiclk<=1b1;
spido<=1b1
dstate<=8d0;
spistate<=idle;
end
default
begin
spics<=1b1;
spiclk<=1b1;
spido<=1b1;
spistate<=idle;
end
endcase
end
2b10://接受數(shù)據(jù)狀態(tài)
begin
case(dstate)//片選信號有效
begin
case (dstate) //片選信號有效
8d0:
begin
spics <= 1b0;
spiclk <= 1b1;
spido <= 1b1;
dstate <= 8d1;
end
8d1:
begin
spics <= 1b0;
spiclk <= 1b1;
spido <= 1b1;
dstate <= 8d2;
end
8d2:
begin
spics <= 1b0;
spiclk <= 1b0;
spido <= 1b1;
dstate <= 8d3;
end
8d3:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d4;
end
8d4:
begin
spics <= 1b0;
spiclk <= 1b0; //緊接著上升沿的下降沿?cái)?shù)據(jù)被讀取
dreceive[7] <= spidi; //接收數(shù)據(jù)最高位
dstate <= 8d5;
end
8d5:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d6;
end
8d6:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[6] <= spidi;
dstate <= 8d7;
end
8d7:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d8;
end
8d8:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[5] <= spidi;
dstate <= 8d9;
end
8d9:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d10;
end
8d10:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[4] <= spidi;
dstate <= 8d11;
end
8d11:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d12;
end
8d12:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[3] <= spidi;
dstate <= 8d13;
end
8d13:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d14;
end
8d14:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[2] <= spidi;
dstate <= 8d15;
end
8d15:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d16;
end
8d16:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[1] <= spidi;
dstate <= 8d17;
end
8d17:
begin
spics <= 1b0;
spiclk <= 1b1;
dstate <= 8d18;
end
8d18:
begin
spics <= 1b0;
spiclk <= 1b0;
dreceive[0] <= spidi; //接收數(shù)據(jù)最低位
dstate <= 8d19;
end
8d19:
begin
spics <= 1b0;
spiclk <= 1b1;
spido <= 1b1;
dstate <= 8d20;
dataout<= dreceive;
end
8d20:
begin
spics <= 1b1; //片選信號無效
spiclk <= 1b1;
spido <= 1b1;
dstate <= 8d0;
spistate <= idle;
end
endcase
end
default:
begin
spics <= 1b1;
spiclk <= 1b1;
spido <= 1b1;
spistate <= idle;
end
endcase //對應(yīng)上面的發(fā)送數(shù)據(jù)情形
end //對應(yīng)上面的RST沒有按下的情形
end //對應(yīng)最上面的always@(posedge clk)
endmodule
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