FPGA控制88E1512 PHY芯片完成网络通信

一、88E1512分析

本文不对88E1512进行详细解析，仅对调试过程中重点使用的几个寄存器进行说明。

1.1 MDIO时序分析

根据手册，MDIO时序中，mdc时钟最高为12Mhz。占空比和建立保持时间要求可以观察上述表格。

MDIO的读数据时序图如下：

MDIO的写数据时序图如下：

各字段表示的含义如下：

1.2 寄存器分析

1.2.1 页地址寄存器

可能是受MDIO寄存器地址字段的位宽限制（5bits），88E1512提供了一个页地址寄存器的功能，可以通过配置任意页的寄存器地址22，实现页的切换，比如从page0，切换到page1,实现远超2^5的寄存器数目的配置。

通过配置此寄存器，可以完成页的切换，实现不同寄存器的读写。

1.2.2 PHY ID寄存器

用于验证MDIO总线是否正常，读取page0的寄存器2，若回读数据时0x141，则证明链路正确。（通过也需要确认MDIO时序中的TA字段，是否应答正确）

1.2.3 MAC特定控制寄存器

本寄存器中，重点关注bit4字段的信息（数据发送时序的控制，有时可能也涉及到bit5字段，数据接收时序的控制），一般FPGA中的MAC会默认增加网络时钟和网络数据的延时，因此88E1512中可以取消其内部的延迟。这个需要根据实际情况进行控制。

以下重点看一下数据发送的时序图。

当bit4字段设置为0时，可以从下面的时序图中看到，此时要求88E1512的引脚上，接收到的时钟和数据的时序关系应该为：在时钟的边沿位置，刚好为数据的稳定位置。即此时FPGA侧若进行了时序上的相位处理，那么88E1512则不需要进行内部的延时，就可以达到时序收敛，稳定的接收到发送数据。

当bit4字段设置为1时，可以从下面的时序图中看到，此时要求88E1512的引脚上，接收到的时钟和数据的时序关系应该为：在时钟的边沿位置，刚好为数据的改变位置。即此时FPGA侧若不进行了时序上的相位处理，时钟和数据为相位对齐关系，那么88E1512则需要进行内部的延时，才可以达到时序收敛，稳定的接收到发送数据。

1.2.4 一般控制器1

从此寄存器中，可以看到，对于88E1512芯片而言，其默认的工作状态为mode[2:0] = 3'b111，保留状态。而我本次需要的工作状态为RGMII to copper，因此需要进行配置使MODE[2:0]= 3'b000，

另外需要注意的是，配置完page6和page18的寄存器时，都需要对芯片进行软复位，即bit15的SC字段，需要设置为1‘b1，88E1512会自动释放复位信号。

二、FPGA的代码实现

2.1 MDIO的时序模块实现

此处也不啰嗦，直接上代码，有兴趣的自行查阅。

`timescale 1ns / 1ps
//
//实现MDC和MDIO时序的SMI接口module phy_smi #(parameter	CLK_FREQ = 100_000_000,//系统时钟频率 100Mparameter	MDC_DIV	= 1000 //MDC分频系数 1000 得到100K时钟
)
(input				clk,input				rst_n,output		reg		mdc,inout				mdio,input		[4:0]	phy_addr, //PHY芯片的地址input		[4:0]	reg_addr, //寄存器地址//wr_req信号上升沿有效input				wr_req,input		[15:0]	wr_data,//rd_req信号上升沿有效input				rd_req,output	reg	[15:0]	rd_data = 16'd0,output	reg			rd_valid = 1'b0,	//接收到的数据有效标志output	reg			rd_error = 1'b0,	//接收数据失败标志output		busy );reg mdc_gen_en = 1'b0; //时钟生成使能，mdc可以不是持续性时钟
reg [15:0] mdc_div_cnt = 0;
wire mdc_pos;//MDC上升沿
wire mdc_neg; //MDC下降沿
wire mdc_hig; //MDC高电平中心位置
wire mdc_low;//MDC低电平中心位置reg	mdio_buf = 1'b0;
reg	mdio_dir = 1'b0;//FPGA是否输出mdio,1'b1表示FPGA控制输出，反之为高阻态//-----------------edge detect---------------------------
reg	wr_req_rise = 1'b0;
reg	wr_req_d0 = 1'b0;
reg	wr_req_d1 = 1'b0;reg	rd_req_rise = 1'b0;
reg	rd_req_d0 = 1'b0;
reg	rd_req_d1 = 1'b0;//---------------------FSM-------------------------------
localparam	[3:0] S_IDLE	= 4'd0;//空闲态
localparam	[3:0] S_PRE_RD	= 4'd1;//前导态
localparam	[3:0] S_RD	= 4'd2;//读状态
localparam	[3:0] S_PRE_WR	= 4'd3;//前导态
localparam	[3:0] S_WR	= 4'd4;//写状态
localparam	[3:0] S_DONE	= 4'd5;//完成态reg		[3:0]	state = S_IDLE;localparam	START_FIELD	= 2'b01; //开始2bits信息，指示开始传输数据
localparam	READ_CODE_FIELD = 2'b10; //读操作码
localparam	WRITE_CODE_FIELD = 2'b01; //写操作码
localparam	TA_FIELD = 2'b10; //turn around。写时，直接发送2'b10即可，读操作时，MDIO控制权交给PHY，此时FPGA的MDIO为高阻reg		[4:0]	bit_cnt;//一次读写正好 32bit Pre + 32bit WR/RDassign mdc_low = (mdc_div_cnt == 16'd0);
assign mdc_hig = (mdc_div_cnt == (MDC_DIV/2) -1);
assign mdc_pos = (mdc_div_cnt == (MDC_DIV/4) -1);
assign mdc_neg = (mdc_div_cnt == (MDC_DIV/2) + (MDC_DIV/4) -1);always @(posedge clk) beginwr_req_d0	<= wr_req;wr_req_d1	<= wr_req_d0;wr_req_rise	<= ~wr_req_d1 & wr_req_d0;rd_req_d0	<= rd_req;rd_req_d1	<= rd_req_d0;rd_req_rise	<= ~rd_req_d1 & rd_req_d0;
endalways @(posedge clk) 
beginif(mdc_gen_en) beginif( mdc_div_cnt <= MDC_DIV - 1)mdc_div_cnt <= mdc_div_cnt + 1'b1;elsemdc_div_cnt <= 0;endelsemdc_div_cnt <= 0;
endalways @(posedge clk) 
beginif(mdc_gen_en) beginif( mdc_pos )mdc <= 1'b1;else if(mdc_neg)mdc <= 1'b0;endelsemdc <= 0;
endalways @(posedge clk or negedge rst_n) 
beginif(~rst_n) beginstate	<= S_IDLE;mdc_gen_en <= 1'b0;rd_valid <= 1'b0;endelse beginrd_valid <= 1'b0;case(state)S_IDLE : beginmdc_gen_en <= 1'b0;bit_cnt <= 0;rd_error <= 1'b0;if(rd_req_rise)state <= S_PRE_RD;else if(wr_req_rise)state <= S_PRE_WR;   endS_PRE_RD : beginmdc_gen_en <= 1'b1;if(mdc_neg) beginif(bit_cnt==5'd31) begin //发送完32个前导1'b1bit_cnt <= 0;state	<= S_RD;endelse beginbit_cnt <= bit_cnt + 1'b1;endend//前导码均为1,FPGA输出mdio_buf <= 1'b1;mdio_dir <= 1'b1;endS_RD : beginmdc_gen_en <= 1'b1;if(mdc_neg) beginif(bit_cnt==5'd31) begin //完成32bits的通信bit_cnt <= 0;state	<= S_DONE;endelse beginbit_cnt <= bit_cnt + 1'b1;endendcase(bit_cnt)5'd0: begin mdio_dir <= 1'b1; mdio_buf	<= START_FIELD[1];end5'd1: begin mdio_dir <= 1'b1; mdio_buf	<= START_FIELD[0];end5'd2: begin mdio_dir <= 1'b1;mdio_buf	<= READ_CODE_FIELD[1];end5'd3: begin mdio_dir <= 1'b1;mdio_buf	<= READ_CODE_FIELD[0];end5'd4: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[4];end5'd5: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[3];end5'd6: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[2];end5'd7: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[1];end5'd8: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[0];end5'd9: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[4];end5'd10: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[3];end5'd11: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[2];end5'd12: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[1];end5'd13: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[0];enddefault: begin mdio_dir <= 1'b0;end endcase//MDC下降沿时取数据if(mdc_neg) begincase(bit_cnt)5'd14: rd_error	<= mdio; //若PHY应答，此处会被拉低，否则失败;5'd15: rd_data[15]	<= mdio;5'd16: rd_data[14]	<= mdio;5'd17: rd_data[13]	<= mdio;5'd18: rd_data[12]	<= mdio;5'd19: rd_data[11]	<= mdio;5'd20: rd_data[10]	<= mdio;5'd21: rd_data[9]	<= mdio;5'd22: rd_data[8]	<= mdio;5'd23: rd_data[7]	<= mdio;5'd24: rd_data[6]	<= mdio;5'd25: rd_data[5]	<= mdio;5'd26: rd_data[4]	<= mdio;5'd27: rd_data[3]	<= mdio;5'd28: rd_data[2]	<= mdio;5'd29: rd_data[1]	<= mdio;5'd30:begin rd_data[0]	<= mdio; rd_valid <= 1'b1;enddefault:;endcaseendendS_PRE_WR : beginmdc_gen_en <= 1'b1;if(mdc_neg) beginif(bit_cnt==5'd31) begin //发送完32个前导1'b1bit_cnt <= 0;state	<= S_WR;endelse beginbit_cnt <= bit_cnt + 1'b1;endend//前导码均为1,FPGA输出mdio_buf <= 1'b1;mdio_dir <= 1'b1;endS_WR : beginmdc_gen_en <= 1'b1;if(mdc_neg) beginif(bit_cnt==5'd31) begin //完成32bits的通信bit_cnt <= 0;state	<= S_DONE;endelse beginbit_cnt <= bit_cnt + 1'b1;endendcase(bit_cnt)5'd0: begin mdio_dir <= 1'b1; mdio_buf	<= START_FIELD[1];end5'd1: begin mdio_dir <= 1'b1; mdio_buf	<= START_FIELD[0];end5'd2: begin mdio_dir <= 1'b1;mdio_buf	<= WRITE_CODE_FIELD[1];end5'd3: begin mdio_dir <= 1'b1;mdio_buf	<= WRITE_CODE_FIELD[0];end5'd4: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[4];end5'd5: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[3];end5'd6: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[2];end5'd7: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[1];end5'd8: begin mdio_dir <= 1'b1;mdio_buf	<= phy_addr[0];end5'd9: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[4];end5'd10: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[3];end5'd11: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[2];end5'd12: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[1];end5'd13: begin mdio_dir <= 1'b1;mdio_buf	<= reg_addr[0];end5'd14: begin mdio_dir <= 1'b1;mdio_buf	<= TA_FIELD[1];end5'd15: begin mdio_dir <= 1'b1;mdio_buf	<= TA_FIELD[0];end5'd16: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[15];end5'd17: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[14];end5'd18: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[13];end5'd19: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[12];end5'd20: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[11];end5'd21: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[10];end5'd22: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[9];end5'd23: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[8];end5'd24: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[7];end5'd25: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[6];end5'd26: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[5];end5'd27: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[4];end5'd28: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[3];end5'd29: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[2];end5'd30: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[1];end5'd31: begin mdio_dir <= 1'b1; mdio_buf	<= wr_data[0];enddefault:;endcaseendS_DONE : beginmdc_gen_en <= 1'b0;state	<= S_IDLE;endendcaseend
endassign busy = (state != S_IDLE);assign mdio = mdio_dir ? mdio_buf : 1'bZ;//wire mdio_in;
//assign mdio_in = mdio;endmodule

2.2 88E1512的控制代码

`timescale 1ns / 1psmodule PHY_88E1512(input clk,input rst_n,output mdc, //inout mdio, //input config_start, //启动88E1512的配置，使FPGA可在RGMII 1G模式下通信output reg link_ok = 1'b0, //读取PHY ID验证链路是否正确output reg link_error = 1'b0, //读取PHY ID验证链路是否正确output reg config_done  //配置完成);localparam PHY_88E1512_ADDR = 5'd0;localparam IDLE_STATE = 4'd0;
localparam ARB_STATE = 4'd1;
localparam LINK_READY_STATE = 4'd2; //读取PHY ID :bit3:18  数值为0x0141即通信链路正常
localparam CFG_READY_STATE = 4'd3;
localparam WR_OP_STATE = 4'd4;
localparam RD_OP_STATE = 4'd5;
localparam LINK_ERR_STATE = 4'd6;
localparam DONE_STATE = 4'd7;reg [3:0] state = IDLE_STATE;reg config_start_d1 = 1'b0;reg [3:0] link_cnt = 4'd0;//链路验证时寄存器计数
reg [3:0] wr_cnt = 4'd0; //写读寄存器计数
reg [15:0] rd_data_latch = 0;//SMI接口信号
//reg [4:0] phy_addr = 5'd0; //PHY芯片的地址
reg [4:0] reg_addr = 5'd0; //寄存器地址//wr_req信号上升沿有效
reg wr_req = 1'b0;
reg [15:0] wr_data = 16'd0;//rd_req信号上升沿有效
reg rd_req = 1'b0;
wire [15:0]rd_data;
wire rd_valid;	//接收到的数据有效标志
wire rd_error;	//接收数据失败标志wire busy ;
reg busy_d1 = 1'b0;always@(posedge clk)
beginbusy_d1 <= busy;
endalways@(posedge clk)
beginconfig_start_d1 <= config_start;
endalways@(posedge clk or negedge rst_n)
beginif(!rst_n) beginstate <= IDLE_STATE;wr_req <= 1'b0;wr_cnt <= 0;rd_req <= 1'b0;link_cnt <= 0;rd_data_latch <= 16'h0;end else begincase(state)IDLE_STATE: beginwr_req <= 1'b0;wr_cnt <= 0;rd_req <= 1'b0;link_cnt <= 0;if(!config_start_d1 & config_start) beginstate <= ARB_STATE;rd_data_latch <= 16'h0;link_ok <= 1'b0;link_error <= 1'b0;config_done <= 1'b0;endendARB_STATE : beginwr_req <= 1'b0;rd_req <= 1'b0;if(link_ok == 1'b0) //先进行链路验证state <= LINK_READY_STATE;else if(config_done == 1'b0) //再配置寄存器state <= CFG_READY_STATE;elsestate <= IDLE_STATE;endLINK_READY_STATE : begincase(link_cnt)4'd0: begin  //首先写寄存器，选中page0link_cnt <= 4'd1;reg_addr <= 5'd22; //寄存器地址22wr_data <= 16'd0;state <= WR_OP_STATE;end4'd1: begin  //其次读取PHY IDlink_cnt <= 4'd2;reg_addr <= 5'd2; //寄存器地址2state <= RD_OP_STATE;end4'd2: begin //验证回读ID是否正确if(rd_data_latch == 16'h0141) beginstate <= ARB_STATE;link_ok <= 1'b1;endelse beginstate <= LINK_ERR_STATE;endenddefault:state <= IDLE_STATE;endcaseendCFG_READY_STATE : beginwr_cnt <= wr_cnt + 4'd1;case(wr_cnt)//-----由于FPGA MAC核已经调整好时序，因此PHY处不需要进行时序延时4'd0: begin  //首先写寄存器，选中page2reg_addr <= 5'd22; //寄存器地址22wr_data <= 16'd2;state <= WR_OP_STATE;end4'd1: begin  //读寄存器reg_addr <= 5'd21; //寄存器地址21state <= RD_OP_STATE;end  4'd2: begin  //取消PHY内部的延时reg_addr <= 5'd21; //寄存器地址21wr_data <= rd_data_latch & 16'hFFEF;//bit4置为0state <= WR_OP_STATE;end      //-----PHY工作在RGMII to Copper模式4'd3: begin  //首先写寄存器，选中page18reg_addr <= 5'd22; //寄存器地址22wr_data <= 16'd18;state <= WR_OP_STATE;end4'd4: begin  //其次配置MODE参数，使PHY工作在RGMII to Copper模式reg_addr <= 5'd20; //寄存器地址20wr_data <= 16'h0;//bit15表示软复位，bit[2:0]表示RGMII to Copper模式，其余为默认值state <= WR_OP_STATE;end4'd5: begin  //其次配置MODE参数，使PHY工作在RGMII to Copper模式reg_addr <= 5'd20; //寄存器地址20wr_data <= 16'h8000;//bit15表示软复位，bit[2:0]表示RGMII to Copper模式，其余为默认值state <= WR_OP_STATE;config_done <= 1'b1;enddefault:state <= IDLE_STATE;endcaseendWR_OP_STATE : beginwr_req <= 1'b1;if(busy_d1 & !busy) //busy下降沿state <= ARB_STATE;endRD_OP_STATE : begin rd_req <= 1'b1;if(rd_valid) beginrd_data_latch <= rd_data;endif(rd_error)state <= LINK_ERR_STATE;else if(busy_d1 & !busy) //busy下降沿state <= ARB_STATE;endLINK_ERR_STATE : beginlink_error <= 1'b1;state <= IDLE_STATE;endDONE_STATE : beginstate <= IDLE_STATE;enddefault : beginstate <= IDLE_STATE;endendcaseend
endphy_smi #(.CLK_FREQ(25_000_000),//系统时钟频率 25M.MDC_DIV(50) //MDC分频系数 50 得到500K时钟
)
phy_smi(.clk(clk),//input				clk,.rst_n(rst_n),//input				rst_n,.mdc(mdc),//output		reg		mdc,.mdio(mdio),//inout				mdio,.phy_addr(PHY_88E1512_ADDR),//input		[4:0]	phy_addr, //PHY芯片的地址.reg_addr(reg_addr),//input		[4:0]	reg_addr, //寄存器地址//wr_req信号上升沿有效.wr_req(wr_req),//input				wr_req,.wr_data(wr_data),//input		[15:0]	wr_data,//rd_req信号上升沿有效.rd_req(rd_req),//input				rd_req,.rd_data(rd_data),//output	reg	[15:0]	rd_data = 16'd0,.rd_valid(rd_valid),//output	reg			rd_valid = 1'b0,	//接收到的数据有效标志.rd_error(rd_error),//output	reg			rd_error = 1'b0,	//接收数据失败标志.busy(busy) //output		busy );
endmodule