669 lines
21 KiB
Markdown
669 lines
21 KiB
Markdown
本文大部分MCU功能是由MCU CORE + 外设IP组成。</br>
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MCU CORE可能是arm cortex系列,51等等再通过内部总线连接在一起。</br>
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内部总线常见的有ARM AMBA(AHB APB等),还有xilinx的AXI。</br>
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AXI-LITE总之就是将ipcore内部的寄存器映射为mcu core能够访问到的寄存器地址</br>
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下面是一个pwm ipcore 的例子</br>
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实现一个简易的pwm非常容易,即通过两个寄存器,这里没有使用单独时钟,直接使用总线时钟来分频</br>
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- 频率计数器
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- 占空比寄存器
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下面提供代码例子</br>
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```
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`timescale 1 ns / 1 ps
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module axi_pwm_v1_0_S00_AXI #
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(
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// Users to add parameters here
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// User parameters ends
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// Do not modify the parameters beyond this line
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// Width of S_AXI data bus
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parameter integer C_S_AXI_DATA_WIDTH = 32,
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// Width of S_AXI address bus
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parameter integer C_S_AXI_ADDR_WIDTH = 4
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)
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(
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// Users to add ports here
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output wire pwm_out,
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output wire [31 : 0] pwn_reg,
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// User ports ends
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// Do not modify the ports beyond this line
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// Global Clock Signal
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input wire S_AXI_ACLK,
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// Global Reset Signal. This Signal is Active LOW
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input wire S_AXI_ARESETN,
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// Write address (issued by master, acceped by Slave)
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input wire [C_S_AXI_ADDR_WIDTH-1 : 0] S_AXI_AWADDR,
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// Write channel Protection type. This signal indicates the
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// privilege and security level of the transaction, and whether
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// the transaction is a data access or an instruction access.
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input wire [2 : 0] S_AXI_AWPROT,
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// Write address valid. This signal indicates that the master signaling
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// valid write address and control information.
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input wire S_AXI_AWVALID,
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// Write address ready. This signal indicates that the slave is ready
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// to accept an address and associated control signals.
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output wire S_AXI_AWREADY,
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// Write data (issued by master, acceped by Slave)
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input wire [C_S_AXI_DATA_WIDTH-1 : 0] S_AXI_WDATA,
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// Write strobes. This signal indicates which byte lanes hold
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// valid data. There is one write strobe bit for each eight
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// bits of the write data bus.
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input wire [(C_S_AXI_DATA_WIDTH/8)-1 : 0] S_AXI_WSTRB,
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// Write valid. This signal indicates that valid write
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// data and strobes are available.
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input wire S_AXI_WVALID,
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// Write ready. This signal indicates that the slave
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// can accept the write data.
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output wire S_AXI_WREADY,
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// Write response. This signal indicates the status
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// of the write transaction.
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output wire [1 : 0] S_AXI_BRESP,
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// Write response valid. This signal indicates that the channel
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// is signaling a valid write response.
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output wire S_AXI_BVALID,
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// Response ready. This signal indicates that the master
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// can accept a write response.
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input wire S_AXI_BREADY,
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// Read address (issued by master, acceped by Slave)
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input wire [C_S_AXI_ADDR_WIDTH-1 : 0] S_AXI_ARADDR,
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// Protection type. This signal indicates the privilege
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// and security level of the transaction, and whether the
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// transaction is a data access or an instruction access.
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input wire [2 : 0] S_AXI_ARPROT,
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// Read address valid. This signal indicates that the channel
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// is signaling valid read address and control information.
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input wire S_AXI_ARVALID,
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// Read address ready. This signal indicates that the slave is
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// ready to accept an address and associated control signals.
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output wire S_AXI_ARREADY,
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// Read data (issued by slave)
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output wire [C_S_AXI_DATA_WIDTH-1 : 0] S_AXI_RDATA,
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// Read response. This signal indicates the status of the
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// read transfer.
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output wire [1 : 0] S_AXI_RRESP,
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// Read valid. This signal indicates that the channel is
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// signaling the required read data.
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output wire S_AXI_RVALID,
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// Read ready. This signal indicates that the master can
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// accept the read data and response information.
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input wire S_AXI_RREADY
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);
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// AXI4LITE signals
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reg [C_S_AXI_ADDR_WIDTH-1 : 0] axi_awaddr;
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reg axi_awready;
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reg axi_wready;
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reg [1 : 0] axi_bresp;
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reg axi_bvalid;
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reg [C_S_AXI_ADDR_WIDTH-1 : 0] axi_araddr;
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reg axi_arready;
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reg [C_S_AXI_DATA_WIDTH-1 : 0] axi_rdata;
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reg [1 : 0] axi_rresp;
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reg axi_rvalid;
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// Example-specific design signals
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// local parameter for addressing 32 bit / 64 bit C_S_AXI_DATA_WIDTH
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// ADDR_LSB is used for addressing 32/64 bit registers/memories
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// ADDR_LSB = 2 for 32 bits (n downto 2)
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// ADDR_LSB = 3 for 64 bits (n downto 3)
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localparam integer ADDR_LSB = (C_S_AXI_DATA_WIDTH/32) + 1;
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localparam integer OPT_MEM_ADDR_BITS = 1;
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//----------------------------------------------
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//-- Signals for user logic register space example
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wire ovprd;
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reg[C_S_AXI_DATA_WIDTH-1:0] pwm_counter;
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wire pre_pwm_out;
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//------------------------------------------------
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//-- Number of Slave Registers 4
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg0;
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg1;
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg2;
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg3;
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wire slv_reg_rden;
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wire slv_reg_wren;
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reg [C_S_AXI_DATA_WIDTH-1:0] reg_data_out;
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integer byte_index;
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// I/O Connections assignments
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assign S_AXI_AWREADY = axi_awready;
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assign S_AXI_WREADY = axi_wready;
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assign S_AXI_BRESP = axi_bresp;
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assign S_AXI_BVALID = axi_bvalid;
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assign S_AXI_ARREADY = axi_arready;
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assign S_AXI_RDATA = axi_rdata;
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assign S_AXI_RRESP = axi_rresp;
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assign S_AXI_RVALID = axi_rvalid;
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// Implement axi_awready generation
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// axi_awready is asserted for one S_AXI_ACLK clock cycle when both
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// S_AXI_AWVALID and S_AXI_WVALID are asserted. axi_awready is
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// de-asserted when reset is low.
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_awready <= 1'b0;
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end
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else
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begin
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if (~axi_awready && S_AXI_AWVALID && S_AXI_WVALID)
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begin
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// slave is ready to accept write address when
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// there is a valid write address and write data
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// on the write address and data bus. This design
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// expects no outstanding transactions.
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axi_awready <= 1'b1;
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end
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else
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begin
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axi_awready <= 1'b0;
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end
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end
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end
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// Implement axi_awaddr latching
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// This process is used to latch the address when both
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// S_AXI_AWVALID and S_AXI_WVALID are valid.
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_awaddr <= 0;
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end
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else
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begin
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if (~axi_awready && S_AXI_AWVALID && S_AXI_WVALID)
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begin
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// Write Address latching
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axi_awaddr <= S_AXI_AWADDR;
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end
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end
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end
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// Implement axi_wready generation
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// axi_wready is asserted for one S_AXI_ACLK clock cycle when both
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// S_AXI_AWVALID and S_AXI_WVALID are asserted. axi_wready is
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// de-asserted when reset is low.
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_wready <= 1'b0;
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end
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else
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begin
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if (~axi_wready && S_AXI_WVALID && S_AXI_AWVALID)
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begin
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// slave is ready to accept write data when
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// there is a valid write address and write data
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// on the write address and data bus. This design
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// expects no outstanding transactions.
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axi_wready <= 1'b1;
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end
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else
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begin
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axi_wready <= 1'b0;
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end
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end
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end
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// Implement memory mapped register select and write logic generation
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// The write data is accepted and written to memory mapped registers when
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// axi_awready, S_AXI_WVALID, axi_wready and S_AXI_WVALID are asserted. Write strobes are used to
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// select byte enables of slave registers while writing.
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// These registers are cleared when reset (active low) is applied.
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// Slave register write enable is asserted when valid address and data are available
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// and the slave is ready to accept the write address and write data.
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assign slv_reg_wren = axi_wready && S_AXI_WVALID && axi_awready && S_AXI_AWVALID;
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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slv_reg0 <= 500;
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slv_reg1 <= 100;
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slv_reg2 <= 0;
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slv_reg3 <= 0;
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end
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else begin
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if (slv_reg_wren)
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begin
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case ( axi_awaddr[ADDR_LSB+OPT_MEM_ADDR_BITS:ADDR_LSB] )
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2'h0:
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for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
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if ( S_AXI_WSTRB[byte_index] == 1 ) begin
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// Respective byte enables are asserted as per write strobes
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// Slave register 0
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slv_reg0[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
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end
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2'h1:
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for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
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if ( S_AXI_WSTRB[byte_index] == 1 ) begin
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// Respective byte enables are asserted as per write strobes
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// Slave register 1
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slv_reg1[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
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end
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2'h2:
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for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
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if ( S_AXI_WSTRB[byte_index] == 1 ) begin
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// Respective byte enables are asserted as per write strobes
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// Slave register 2
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slv_reg2[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
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end
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2'h3:
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for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
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if ( S_AXI_WSTRB[byte_index] == 1 ) begin
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// Respective byte enables are asserted as per write strobes
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// Slave register 3
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slv_reg3[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
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end
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default : begin
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slv_reg0 <= slv_reg0;
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slv_reg1 <= slv_reg1;
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slv_reg2 <= slv_reg2;
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slv_reg3 <= slv_reg3;
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end
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endcase
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end
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end
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end
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// Implement write response logic generation
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// The write response and response valid signals are asserted by the slave
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// when axi_wready, S_AXI_WVALID, axi_wready and S_AXI_WVALID are asserted.
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// This marks the acceptance of address and indicates the status of
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// write transaction.
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_bvalid <= 0;
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axi_bresp <= 2'b0;
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end
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else
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begin
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if (axi_awready && S_AXI_AWVALID && ~axi_bvalid && axi_wready && S_AXI_WVALID)
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begin
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// indicates a valid write response is available
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axi_bvalid <= 1'b1;
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axi_bresp <= 2'b0; // 'OKAY' response
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end // work error responses in future
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else
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begin
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if (S_AXI_BREADY && axi_bvalid)
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//check if bready is asserted while bvalid is high)
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//(there is a possibility that bready is always asserted high)
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begin
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axi_bvalid <= 1'b0;
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end
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end
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end
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end
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// Implement axi_arready generation
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// axi_arready is asserted for one S_AXI_ACLK clock cycle when
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// S_AXI_ARVALID is asserted. axi_awready is
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// de-asserted when reset (active low) is asserted.
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// The read address is also latched when S_AXI_ARVALID is
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// asserted. axi_araddr is reset to zero on reset assertion.
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_arready <= 1'b0;
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axi_araddr <= 32'b0;
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end
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else
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begin
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if (~axi_arready && S_AXI_ARVALID)
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begin
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// indicates that the slave has acceped the valid read address
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axi_arready <= 1'b1;
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// Read address latching
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axi_araddr <= S_AXI_ARADDR;
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end
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else
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begin
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axi_arready <= 1'b0;
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end
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end
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end
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// Implement axi_arvalid generation
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// axi_rvalid is asserted for one S_AXI_ACLK clock cycle when both
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// S_AXI_ARVALID and axi_arready are asserted. The slave registers
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// data are available on the axi_rdata bus at this instance. The
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// assertion of axi_rvalid marks the validity of read data on the
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// bus and axi_rresp indicates the status of read transaction.axi_rvalid
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// is deasserted on reset (active low). axi_rresp and axi_rdata are
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// cleared to zero on reset (active low).
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_rvalid <= 0;
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axi_rresp <= 0;
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end
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else
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begin
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if (axi_arready && S_AXI_ARVALID && ~axi_rvalid)
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begin
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// Valid read data is available at the read data bus
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axi_rvalid <= 1'b1;
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axi_rresp <= 2'b0; // 'OKAY' response
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end
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else if (axi_rvalid && S_AXI_RREADY)
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begin
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// Read data is accepted by the master
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axi_rvalid <= 1'b0;
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end
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end
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end
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// Implement memory mapped register select and read logic generation
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// Slave register read enable is asserted when valid address is available
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// and the slave is ready to accept the read address.
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assign slv_reg_rden = axi_arready & S_AXI_ARVALID & ~axi_rvalid;
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always @(*)
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begin
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// Address decoding for reading registers
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case ( axi_araddr[ADDR_LSB+OPT_MEM_ADDR_BITS:ADDR_LSB] )
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2'h0 : reg_data_out <= slv_reg0;
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2'h1 : reg_data_out <= slv_reg1;
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2'h2 : reg_data_out <= slv_reg2;
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2'h3 : reg_data_out <= slv_reg3;
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default : reg_data_out <= 0;
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endcase
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end
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// Output register or memory read data
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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axi_rdata <= 0;
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end
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else
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begin
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// When there is a valid read address (S_AXI_ARVALID) with
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// acceptance of read address by the slave (axi_arready),
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// output the read dada
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if (slv_reg_rden)
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begin
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axi_rdata <= reg_data_out; // register read data
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end
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end
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end
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// Add user logic here
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always @(posedge S_AXI_ACLK)
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begin
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if(S_AXI_ARESETN == 1'b0 || ovprd)
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pwm_counter = 0;
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else
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pwm_counter = pwm_counter +1;
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end
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assign ovprd = (pwm_counter[31:0] < slv_reg0[31:0])? 1'b0 : 1'b1;
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assign pre_pwm_out = (slv_reg1[31:0] < pwm_counter)? 1'b0:1'b1;
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assign pwm_out = pre_pwm_out;
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assign pwn_reg = pwm_counter;
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// User logic ends
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endmodule
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```
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上面例子在官方axi-lite模板修改，主要改动
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1. 添加ip核寄存器
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```
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//-- Number of Slave Registers 4
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg0;
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reg [C_S_AXI_DATA_WIDTH-1:0] slv_reg1;
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```
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2. 写入逻辑实现
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```
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assign slv_reg_wren = axi_wready && S_AXI_WVALID && axi_awready && S_AXI_AWVALID;
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always @( posedge S_AXI_ACLK )
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begin
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if ( S_AXI_ARESETN == 1'b0 )
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begin
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slv_reg0 <= 500;
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slv_reg1 <= 100;
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slv_reg2 <= 0;
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slv_reg3 <= 0;
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end
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else begin
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if (slv_reg_wren)
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begin
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case ( axi_awaddr[ADDR_LSB+OPT_MEM_ADDR_BITS:ADDR_LSB] )
|
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2'h0:
|
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for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
|
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if ( S_AXI_WSTRB[byte_index] == 1 ) begin
|
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// Respective byte enables are asserted as per write strobes
|
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// Slave register 0
|
||
slv_reg0[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
|
||
end
|
||
2'h1:
|
||
for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
|
||
if ( S_AXI_WSTRB[byte_index] == 1 ) begin
|
||
// Respective byte enables are asserted as per write strobes
|
||
// Slave register 1
|
||
slv_reg1[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
|
||
end
|
||
2'h2:
|
||
for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
|
||
if ( S_AXI_WSTRB[byte_index] == 1 ) begin
|
||
// Respective byte enables are asserted as per write strobes
|
||
// Slave register 2
|
||
slv_reg2[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
|
||
end
|
||
2'h3:
|
||
for ( byte_index = 0; byte_index <= (C_S_AXI_DATA_WIDTH/8)-1; byte_index = byte_index+1 )
|
||
if ( S_AXI_WSTRB[byte_index] == 1 ) begin
|
||
// Respective byte enables are asserted as per write strobes
|
||
// Slave register 3
|
||
slv_reg3[(byte_index*8) +: 8] <= S_AXI_WDATA[(byte_index*8) +: 8];
|
||
end
|
||
default : begin
|
||
slv_reg0 <= slv_reg0;
|
||
slv_reg1 <= slv_reg1;
|
||
slv_reg2 <= slv_reg2;
|
||
slv_reg3 <= slv_reg3;
|
||
end
|
||
endcase
|
||
end
|
||
end
|
||
end
|
||
```
|
||
|
||
2. 内存地址i映射
|
||
|
||
|
||
```
|
||
// Implement memory mapped register select and read logic generation
|
||
// Slave register read enable is asserted when valid address is available
|
||
// and the slave is ready to accept the read address.
|
||
assign slv_reg_rden = axi_arready & S_AXI_ARVALID & ~axi_rvalid;
|
||
always @(*)
|
||
begin
|
||
// Address decoding for reading registers
|
||
case ( axi_araddr[ADDR_LSB+OPT_MEM_ADDR_BITS:ADDR_LSB] )
|
||
2'h0 : reg_data_out <= slv_reg0;
|
||
2'h1 : reg_data_out <= slv_reg1;
|
||
2'h2 : reg_data_out <= slv_reg2;
|
||
2'h3 : reg_data_out <= slv_reg3;
|
||
default : reg_data_out <= 0;
|
||
endcase
|
||
end
|
||
|
||
```
|
||
|
||
3. 读取逻辑实现
|
||
|
||
```
|
||
|
||
// Output register or memory read data
|
||
always @( posedge S_AXI_ACLK )
|
||
begin
|
||
if ( S_AXI_ARESETN == 1'b0 )
|
||
begin
|
||
axi_rdata <= 0;
|
||
end
|
||
else
|
||
begin
|
||
// When there is a valid read address (S_AXI_ARVALID) with
|
||
// acceptance of read address by the slave (axi_arready),
|
||
// output the read dada
|
||
if (slv_reg_rden)
|
||
begin
|
||
axi_rdata <= reg_data_out; // register read data
|
||
end
|
||
end
|
||
end
|
||
|
||
```
|
||
|
||
6. 用户逻辑的实现
|
||
7.
|
||
```
|
||
// Add user logic here
|
||
always @(posedge S_AXI_ACLK)
|
||
begin
|
||
if(S_AXI_ARESETN == 1'b0 || ovprd)
|
||
pwm_counter = 0;
|
||
else
|
||
pwm_counter = pwm_counter +1;
|
||
end
|
||
assign ovprd = (pwm_counter[31:0] < slv_reg0[31:0])? 1'b0 : 1'b1;
|
||
assign pre_pwm_out = (slv_reg1[31:0] < pwm_counter)? 1'b0:1'b1;
|
||
assign pwm_out = pre_pwm_out;
|
||
assign pwn_reg = pwm_counter;
|
||
```
|
||
|
||
pwm的实现逻辑非常简单,输出频率由pwm_counter控制，pwm_counter > slv_reg0[31:0]时复位pwm_counter。</br>
|
||
占空比由于(slv_reg1[31:0] < pwm_counter)控制</br>
|
||
通过控制占空比来是
|
||
|
||
#### 在fpga板子上实际测试
|
||
|
||
|
||
|
||
</br>
|
||
|
||
板级设计
|
||
</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
- axi_pwm_v1_0_S00_AXI_0 是本文描述的自定义的ipcore
|
||
- ps7_0_axi_periph 是axi-full到axi lite的退化core
|
||
- systemila用于调试axi-lite总线
|
||
|
||
|
||
|
||
#### 真机调试axi-lite
|
||
|
||
通过systemila来调试</br>
|
||
出发条件选择为RLast both edge 即观测接收数据</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
编写调试代码
|
||
|
||
```
|
||
#include <stdio.h>
|
||
#include "platform.h"
|
||
#include "xil_printf.h"
|
||
#include "xil_io.h"
|
||
#include "xil_types.h"
|
||
|
||
int main()
|
||
{
|
||
init_platform();
|
||
|
||
u32 t0 = Xil_In32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x00);
|
||
u32 t1 = Xil_In32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x04);
|
||
u32 t2 = Xil_In32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x08);
|
||
|
||
|
||
print("Hello World\n\r");
|
||
print("Successfully ran Hello World application");
|
||
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x00,500);
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x04,300);
|
||
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x00,200);
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x04,50);
|
||
|
||
cleanup_platform();
|
||
return 0;
|
||
}
|
||
```
|
||
运行到
|
||
` u32 t2 = Xil_In32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x08);`
|
||
|
||
时出现波形</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
|
||
#### 调试pwm
|
||
通过改变寄存器1和寄存器2的值来改变占空比
|
||
|
||
```
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x00,500);
|
||
Xil_Out32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x04,300);
|
||
```
|
||
|
||
寄存器1 500 2: 100</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
寄存器1 500 2: 300</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
</br>
|
||
|
||
寄存器1 200 2: 50</br>
|
||
|
||
|
||
|
||
</br>
|
||
|
||
#### 问题
|
||
|
||
访问非4字节对齐地址会抛出异常，如</br>
|
||
```
|
||
Xil_In32(XPAR_AXI_PWM_V1_0_S00_AXI_0_BASEADDR + 0x01);
|
||
```
|
||
|
||
|