前情回顾
（1）ZYNQ中PS端MIO操作
（2）ZYNQ中PS端MIO中断
（3）ZYNQ中PS端UART通信
（4）ZYNQ中PS端XADC读取
1. 读写DDR底层结构 zynq 7000 SOC的HP口是High-Performance Ports的缩写，如下图所示，一共有4个HP接口，HP接口是AXI Slave设备，我们可以通过这4个HP接口实现高带宽的数据交互。实现PL读写PS端挂载的DDR需要使用HP接口。
如下图所示，选择HP0 interface。
使用的时钟是150Mhz，HP的带宽是150Mhz * 64bit，对于视频处理，ADC数据采集等应用都有足够的带宽。如下图所示，配置完HP端口以后，zynq会多出一个AXI Slave端口，名称为S_AXI_HP0，不过这些端口都是AXI3标准的，我们常用的是AXI4协议，这里添加1个AXI Interconnect IP，用于协议转换（AXI3<->AXI4）。设置S00_AXI端口为AXI4协议。
2. PL端AXI MASTER的机制
AXI4所采用的是一种READY，VALID握手通信机制，即主从模块进行数据通信前，先根据操作对各所用到的数据、地址通道进行握手。主要操作包括传输发送者A等到传输接受者B的READY信号后，A将数据与VALID信号同时发送给B，这是一种典型的握手机制。
AXI总线分为五个通道：
读地址通道，包含ARVALID, ARADDR, ARREADY信号；
写地址通道，包含AWVALID，AWADDR, AWREADY信号；
读数据通道，包含RVALID, RDATA, RREADY, RRESP信号；
写数据通道，包含WVALID, WDATA，WSTRB, WREADY信号；
写应答通道，包含BVALID, BRESP, BREADY信号；
系统通道，包含：ACLK，ARESETN信号；
其中ACLK为axi总线时钟，ARESETN是axi总线复位信号，低电平有效；读写数据与读写地址类信号宽度都为32bit；READY与VALID是对应的通道握手信号；WSTRB信号为1的bit对应WDATA有效数据字节，WSTRB宽度是32bit/8=4bit；BRESP与RRESP分别为写回应信号，读回应信号，宽度都为2bit，‘h0代表成功，其他为错误。
读操作顺序为主与从进行读地址通道握手并传输地址内容，然后在读数据通道握手并传输所读内容以及读取操作的回应，时钟上升沿有效。如图所示：
写操作顺序为主与从进行写地址通道握手并传输地址内容，然后在写数据通道握手并传输所读内容，最后再写回应通道握手，并传输写回应数据，时钟上升沿有效。如图所示：
附录代码清单：
moduleaq_axi_master(
// Reset, Clock
input ARESETN,
input ACLK,
// Master 写地址通道
output [0:0] M_AXI_AWID,
output [31:0] M_AXI_AWADDR,
output [7:0] M_AXI_AWLEN, // Burst Length:0-255
output [2:0] M_AXI_AWSIZE, // Burst Size:Fixed 2'b011
output [1:0] M_AXI_AWBURST, // Burst Type:Fixed 2'b01(Incremental Burst)
output M_AXI_AWLOCK, // Lock: Fixed2'b00
output [3:0] M_AXI_AWCACHE, // Cache: Fiex2'b0011
output [2:0] M_AXI_AWPROT, // Protect: Fixed2'b000
output [3:0] M_AXI_AWQOS, // QoS: Fixed2'b0000
output [0:0] M_AXI_AWUSER, // User: Fixed32'd0
output M_AXI_AWVALID,
input M_AXI_AWREADY,
// Master 写数据通道
output [63:0] M_AXI_WDATA,
output [7:0] M_AXI_WSTRB,
output M_AXI_WLAST,
output [0:0] M_AXI_WUSER,
output M_AXI_WVALID,
input M_AXI_WREADY,
// Master 写响应通道
input [0:0] M_AXI_BID,
input [1:0] M_AXI_BRESP,
input [0:0] M_AXI_BUSER,
input M_AXI_BVALID,
output M_AXI_BREADY,
// Master 读地址通道
output [0:0] M_AXI_ARID,
output [31:0] M_AXI_ARADDR,
output [7:0] M_AXI_ARLEN,
output [2:0] M_AXI_ARSIZE,
output [1:0] M_AXI_ARBURST,
output [1:0] M_AXI_ARLOCK,
output [3:0] M_AXI_ARCACHE,
output [2:0] M_AXI_ARPROT,
output [3:0] M_AXI_ARQOS,
output [0:0] M_AXI_ARUSER,
output M_AXI_ARVALID,
input M_AXI_ARREADY,
// Master 读数据通道
input [0:0] M_AXI_RID,
input [63:0] M_AXI_RDATA,
input [1:0] M_AXI_RRESP,
input M_AXI_RLAST,
input [0:0] M_AXI_RUSER,
input M_AXI_RVALID,
output M_AXI_RREADY,
// Local Bus
input MASTER_RST,
input WR_START,
input [31:0] WR_ADRS,
input [31:0] WR_LEN,
output WR_READY,
output WR_FIFO_RE,
input WR_FIFO_EMPTY,
input WR_FIFO_AEMPTY,
input [63:0] WR_FIFO_DATA,
output WR_DONE,
input RD_START,
input [31:0] RD_ADRS,
input [31:0] RD_LEN,
output RD_READY,
output RD_FIFO_WE,
input RD_FIFO_FULL,
input RD_FIFO_AFULL,
output [63:0] RD_FIFO_DATA,
output RD_DONE,
output [31:0] DEBUG
);
localparam S_WR_IDLE = 3'd0;
localparam S_WA_WAIT = 3'd1;
localparam S_WA_START = 3'd2;
localparam S_WD_WAIT = 3'd3;
localparam S_WD_PROC = 3'd4;
localparam S_WR_WAIT = 3'd5;
localparam S_WR_DONE = 3'd6;
reg [2:0] wr_state;
reg [31:0] reg_wr_adrs;
reg [31:0] reg_wr_len;
reg reg_awvalid, reg_wvalid, reg_w_last;
reg [7:0] reg_w_len;
reg [7:0] reg_w_stb;
reg [1:0] reg_wr_status;
reg [3:0] reg_w_count, reg_r_count;
reg [7:0] rd_chkdata, wr_chkdata;
reg [1:0] resp;
reg rd_first_data;
reg rd_fifo_enable;
reg[31:0] rd_fifo_cnt;
assign WR_DONE =(wr_state == S_WR_DONE);
assignWR_FIFO_RE = rd_first_data |(reg_wvalid & ~WR_FIFO_EMPTY & M_AXI_WREADY & rd_fifo_enable);
always @(posedgeACLK or negedge ARESETN)
begin
if(!ARESETN)
rd_fifo_cnt <= 32'd0;
else if(WR_FIFO_RE)
rd_fifo_cnt <= rd_fifo_cnt 32'd1;
else if(wr_state == S_WR_IDLE)
rd_fifo_cnt <= 32'd0;
end
always @(posedgeACLK or negedge ARESETN)
begin
if(!ARESETN)
rd_fifo_enable <= 1'b0;
else if(wr_state == S_WR_IDLE &&WR_START)
rd_fifo_enable <= 1'b1;
else if(WR_FIFO_RE && (rd_fifo_cnt== RD_LEN[31:3] - 32'd1) )
rd_fifo_enable <= 1'b0;
end
// Write State
always @(posedge ACLK or negedge ARESETN)begin
if(!ARESETN) begin
wr_state <= S_WR_IDLE;
reg_wr_adrs[31:0] <= 32'd0;
reg_wr_len[31:0] <= 32'd0;
reg_awvalid <= 1'b0;
reg_wvalid <= 1'b0;
reg_w_last <= 1'b0;
reg_w_len[7:0] <= 8'd0;
reg_w_stb[7:0] <= 8'd0;
reg_wr_status[1:0] <= 2'd0;
reg_w_count[3:0] <= 4'd0;
reg_r_count[3:0] <= 4'd0;
wr_chkdata <= 8'd0;
rd_chkdata <= 8'd0;
resp <= 2'd0;
rd_first_data <= 1'b0;
end else begin
if(MASTER_RST) begin
wr_state <= S_WR_IDLE;
end else begin
case(wr_state)
S_WR_IDLE: begin
if(WR_START) begin //外部开始写地址
wr_state <= S_WA_WAIT;
reg_wr_adrs[31:0] <=WR_ADRS[31:0];//写地址
reg_wr_len[31:0] <= WR_LEN[31:0] -32'd1;//写长度
rd_first_data <= 1'b1;
end
reg_awvalid <= 1'b0;
reg_wvalid <= 1'b0;
reg_w_last <= 1'b0;
reg_w_len[7:0] <= 8'd0;
reg_w_stb[7:0] <= 8'd0;
reg_wr_status[1:0] <= 2'd0;
end
//写地址等待
S_WA_WAIT: begin
//外部FIFO不空或者长度为0则开始写地址
if(!WR_FIFO_AEMPTY |(reg_wr_len[31:11] == 21'd0)) begin
wr_state <= S_WA_START;
end
rd_first_data <= 1'b0;
end
//写地址开始
S_WA_START: begin
wr_state <= S_WD_WAIT;//写数据等待
reg_awvalid <= 1'b1;
//写长度减一
reg_wr_len[31:11] <= reg_wr_len[31:11] - 21'd1;
if(reg_wr_len[31:11] != 21'd0) begin
reg_w_len[7:0] <= 8'hFF;//每次写256个数据
reg_w_last <= 1'b0;
reg_w_stb[7:0] <= 8'hFF;
end else begin//最后不足256个的数据写入
reg_w_len[7:0] <= reg_wr_len[10:3];
reg_w_last <= 1'b1;
reg_w_stb[7:0] <= 8'hFF;
end
end
S_WD_WAIT: begin
//等待写总线READY，进入写数据状态
if(M_AXI_AWREADY) begin
wr_state <= S_WD_PROC;
reg_awvalid <= 1'b0;
//开始写数据
reg_wvalid <= 1'b1;
end
end
//写数据
S_WD_PROC: begin
if(M_AXI_WREADY & ~WR_FIFO_EMPTY)begin
//一次突发写完成
if(reg_w_len[7:0] == 8'd0) begin
wr_state <= S_WR_WAIT;
reg_wvalid <= 1'b0;
reg_w_stb[7:0] <= 8'h00;
end else begin
reg_w_len[7:0] <= reg_w_len[7:0] -8'd1;
end
end
end
//写等待
S_WR_WAIT: begin
//写响应完成
if(M_AXI_BVALID) begin
reg_wr_status[1:0] <= reg_wr_status[1:0] | M_AXI_BRESP[1:0];
if(reg_w_last) begin//写完成
wr_state <= S_WR_DONE;
end else begin//写未完成
wr_state <= S_WA_WAIT;
//地址每次递增
reg_wr_adrs[31:0] <=reg_wr_adrs[31:0] 32'd2048;
end
end
end
S_WR_DONE: begin
wr_state <= S_WR_IDLE;
end
default: begin
wr_state <= S_WR_IDLE;
end
endcase
end
end
end
assign M_AXI_AWID = 1'b0;
assign M_AXI_AWADDR[31:0] =reg_wr_adrs[31:0];
assign M_AXI_AWLEN[7:0] = reg_w_len[7:0];
assign M_AXI_AWSIZE[2:0] = 2'b011;
assign M_AXI_AWBURST[1:0] = 2'b01;
assign M_AXI_AWLOCK = 1'b0;
assign M_AXI_AWCACHE[3:0] = 4'b0011;
assign M_AXI_AWPROT[2:0] = 3'b000;
assign M_AXI_AWQOS[3:0] = 4'b0000;
assign M_AXI_AWUSER[0] = 1'b1;
assign M_AXI_AWVALID = reg_awvalid;
assign M_AXI_WDATA[63:0] = WR_FIFO_DATA[63:0];
assign M_AXI_WSTRB[7:0] = (reg_wvalid & ~WR_FIFO_EMPTY)?8'hFF:8'h00;
assign M_AXI_WLAST = (reg_w_len[7:0] == 8'd0)?1'b1:1'b0;
assign M_AXI_WUSER = 1;
assign M_AXI_WVALID = reg_wvalid & ~WR_FIFO_EMPTY;
assign M_AXI_BREADY = M_AXI_BVALID;
assign WR_READY = (wr_state == S_WR_IDLE)?1'b1:1'b0;
localparam S_RD_IDLE = 3'd0;
localparam S_RA_WAIT = 3'd1;
localparam S_RA_START = 3'd2;
localparam S_RD_WAIT = 3'd3;
localparam S_RD_PROC = 3'd4;
localparam S_RD_DONE = 3'd5;
reg [2:0] rd_state;
reg[31:0] reg_rd_adrs;
reg [31:0] reg_rd_len;
reg reg_arvalid, reg_r_last;
reg [7:0] reg_r_len;
assign RD_DONE = (rd_state == S_RD_DONE) ;
// Read State
always @(posedge ACLK or negedge ARESETN)begin
if(!ARESETN) begin
rd_state <= S_RD_IDLE;
reg_rd_adrs[31:0] <= 32'd0;
reg_rd_len[31:0] <= 32'd0;
reg_arvalid <= 1'b0;
reg_r_len[7:0] <= 8'd0;
end else begin
case(rd_state)
S_RD_IDLE: begin
//读开始
if(RD_START) begin
rd_state <= S_RA_WAIT;
reg_rd_adrs[31:0] <=RD_ADRS[31:0];
reg_rd_len[31:0] <= RD_LEN[31:0] -32'd1;
end
reg_arvalid <= 1'b0;
reg_r_len[7:0] <= 8'd0;
end
//读通道等待
S_RA_WAIT: begin
if(~RD_FIFO_AFULL) begin
rd_state <= S_RA_START;
end
end
//读地址开始
S_RA_START: begin
rd_state <= S_RD_WAIT;
reg_arvalid <= 1'b1;
reg_rd_len[31:11] <=reg_rd_len[31:11] -21'd1;
if(reg_rd_len[31:11] != 21'd0) begin
reg_r_last <= 1'b0;
reg_r_len[7:0] <= 8'd255;
end else begin
reg_r_last <= 1'b1;
reg_r_len[7:0] <= reg_rd_len[10:3];
end
end
//读数据等待
S_RD_WAIT: begin
if(M_AXI_ARREADY) begin
rd_state <= S_RD_PROC;
reg_arvalid <= 1'b0;
end
end
//读数据开始
S_RD_PROC: begin
if(M_AXI_RVALID) begin
if(M_AXI_RLAST) begin
if(reg_r_last) begin
rd_state <= S_RD_DONE;
end else begin
rd_state <= S_RA_WAIT;
reg_rd_adrs[31:0] <=reg_rd_adrs[31:0] 32'd2048;
end
end else begin
reg_r_len[7:0] <=reg_r_len[7:0] -8'd1;
end
end
end
S_RD_DONE:begin
rd_state <= S_RD_IDLE;
end
endcase
end
end
// Master Read Address
assign M_AXI_ARID = 1'b0;
assign M_AXI_ARADDR[31:0] =reg_rd_adrs[31:0];
assign M_AXI_ARLEN[7:0] = reg_r_len[7:0];
assign M_AXI_ARSIZE[2:0] = 3'b011;
assign M_AXI_ARBURST[1:0] = 2'b01;
assign M_AXI_ARLOCK = 1'b0;
assign M_AXI_ARCACHE[3:0] = 4'b0011;
assign M_AXI_ARPROT[2:0] = 3'b000;
assign M_AXI_ARQOS[3:0] = 4'b0000;
assign M_AXI_ARUSER[0] = 1'b1;
assignM_AXI_ARVALID = reg_arvalid;
assign M_AXI_RREADY = M_AXI_RVALID & ~RD_FIFO_FULL;
assign RD_READY = (rd_state == S_RD_IDLE)?1'b1:1'b0;
assign RD_FIFO_WE = M_AXI_RVALID;
assign RD_FIFO_DATA[63:0] = M_AXI_RDATA[63:0];
assign DEBUG[31:0] = {reg_wr_len[31:8],
1'd0, wr_state[2:0],1'd0, rd_state[2:0]};
endmodule
