来源：spi_master.v
`timescale 1ns / 1ps //////////////////////////////////////////////////////////////////////////////// //// //// //// Project Name: ASYNCHRONOUS SPI MASTER (Verilog) //// //// //// //// Module Name: spi_master //// //// //// //// //// //// Author(s): //// //// Iulian Gheorghiu //// //// //// //// Create Date: 01/17/2017 11:21:57 AM //// //// Refer to simulate.v for more information //// //// Revision 0.01 - File Created //// //// //// //////////////////////////////////////////////////////////////////////////////// module spi_master #( parameter WORD_LEN = 8, parameter PRESCALLER_SIZE = 8 )( input rst,/* Asynchronus reset, is mandatory to provide this signal, active on posedge (input) */ input clk,/* Peripheral clock/not necessary to be core clock, the core clock can be different (input) */ ////inout [WORD_LEN - 1:0]bus,/* In/Out data(bidirectional) */ ////TODO input [WORD_LEN - 1:0]data_in, //// In data output [WORD_LEN - 1:0]data_out, //// Out data input wr,/* Send data, asynchronus with 'clk' , active on posedge or negedge(input) */ input rd,/* Read data, , asynchronus with 'clk' , active on posedge or negedge (input) */ output buffempty,/* '1' if transmit buffer is empty (output) */ input [2:0]prescaller,/* The prescaller divider is = (1 << prescaller) value between 0 and 7 for dividers by:1,2,4,8,16,32,64,128 and 256 (input)*/ output sck,/* SPI 'sck' signal (output) */ output mosi,/* SPI 'mosi' signal (output) */ input miso,/* SPI 'miso' signal (input) */ output reg ss,/* SPI 'ss' signal (if send buffer is maintained full the ss signal will not go high between between transmit chars)(output) */ input lsbfirst,/* If '0' msb is send first, if '1' lsb is send first (input) */ input [1:0]mode,/* All four modes is supported (input) */ output reg senderr,/* If you try to send a character if send buffer is full this bit is set to '1', this can be ignored and if is '1' does not affect the interface (output) */ input res_senderr,/* To reset 'senderr' signal write '1' wait minimum half core clock and and after '0' to this bit, is asynchronous with 'clk' (input)*/ output charreceived/* Is set to '1' if a character is received, if you read the receive buffe this bit will go '0', if you ignore it and continue to send data this bit will remain '1' until you read the read register (output) */ ); reg _mosi; reg charreceivedp; reg charreceivedn; reg inbufffullp = 1'b0; reg inbufffulln = 1'b0; reg [WORD_LEN - 1:0]input_buffer; reg [WORD_LEN - 1:0]output_buffer; assign buffempty = ~(inbufffullp ^ inbufffulln); reg [2:0]prescallerbuff; /***********************************************/ /************* Asynchronus send ****************/ /***********************************************/ /* * You need to put the data on the bus and wait a half of core clock to assert the wr signal(see simulation). */ `ifdef WRITE_ON_NEG_EDGE == 1 always @ (negedge wr) `else always @ (posedge wr) `endif begin if(wr && inbufffullp == inbufffulln && buffempty) begin ////input_buffer <= bus; input_buffer <= data_in; //// end end `ifdef WRITE_ON_NEG_EDGE == 1 always @ (negedge wr or posedge res_senderr or posedge rst) `else always @ (posedge wr or posedge res_senderr or posedge rst) `endif begin if(rst) begin inbufffullp <= 1'b0; senderr <= 1'b0; prescallerbuff <= 3'b000; end else if(res_senderr) senderr <= 1'b0; else if(wr && inbufffullp == inbufffulln && buffempty) begin inbufffullp <= ~inbufffullp; prescallerbuff <= prescaller; end else if(!buffempty) senderr <= 1'b1; end /***********************************************/ /************ !Asynchronus send ****************/ /***********************************************/ localparam state_idle = 1'b0; localparam state_busy = 1'b1; reg state; reg [PRESCALLER_SIZE - 1:0]prescaller_cnt; reg [WORD_LEN - 1:0]shift_reg_out; reg [WORD_LEN - 1:0]shift_reg_in; reg [4:0]sckint; //reg sckintn; reg [2:0]prescallerint; reg [7:0]prescdemux; always @ (*) begin if(prescallerint < PRESCALLER_SIZE) begin case(prescallerint) 3'b000: prescdemux <= 8'b00000001; 3'b001: prescdemux <= 8'b00000011; 3'b010: prescdemux <= 8'b00000111; 3'b011: prescdemux <= 8'b00001111; 3'b100: prescdemux <= 8'b00011111; 3'b101: prescdemux <= 8'b00111111; 3'b110: prescdemux <= 8'b01111111; 3'b111: prescdemux <= 8'b11111111; endcase end else prescdemux <= 8'b00000001; end reg lsbfirstint; reg [1:0]modeint; always @ (posedge clk or posedge rst) begin if(rst) begin inbufffulln <= 1'b0; ss <= 1'b1; state <= state_idle; prescaller_cnt <= {PRESCALLER_SIZE{1'b0}}; prescallerint <= {PRESCALLER_SIZE{3'b0}}; shift_reg_out <= {WORD_LEN{1'b0}}; shift_reg_in <= {WORD_LEN{1'b0}}; sckint <= {5{1'b0}}; _mosi <= 1'b1; output_buffer <= {WORD_LEN{1'b0}}; charreceivedp <= 1'b0; lsbfirstint <= 1'b0; modeint <= 2'b00; end else begin case(state) state_idle: begin if(inbufffullp != inbufffulln) begin inbufffulln <= ~inbufffulln; ss <= 1'b0; prescaller_cnt <= {PRESCALLER_SIZE{1'b0}}; prescallerint <= prescallerbuff; lsbfirstint <= lsbfirst; modeint <= mode; shift_reg_out <= input_buffer; state <= state_busy; if(!mode[0]) begin if(!lsbfirst) _mosi <= input_buffer[WORD_LEN - 1]; else _mosi <= input_buffer[0]; end end end state_busy: begin if(prescaller_cnt != prescdemux) begin prescaller_cnt <= prescaller_cnt + 1; end else begin prescaller_cnt <= {PRESCALLER_SIZE{1'b0}}; sckint <= sckint + 1; if(sckint[0] == modeint[0]) begin if(!lsbfirstint) begin shift_reg_in <= {miso, shift_reg_in[7:1]}; shift_reg_out <= {shift_reg_out[6:0], 1'b1}; end else begin shift_reg_in <= {shift_reg_in[6:0], miso}; shift_reg_out <= {1'b1, shift_reg_out[7:1]}; end end else begin if(sckint[4:1] == WORD_LEN - 1) begin sckint <= {5{1'b0}}; if(inbufffullp == inbufffulln) begin ss <= 1'b1; end output_buffer <= shift_reg_in; if(charreceivedp == charreceivedn) charreceivedp <= ~charreceivedp; state <= state_idle; end else begin if(!lsbfirstint) _mosi <= shift_reg_out[WORD_LEN - 1]; else _mosi <= shift_reg_out[0]; end end end end endcase end end /* * You need to assert rd signal, wait a half core clock and after read the data(see simulation). */ `ifdef READ_ON_NEG_EDGE == 1 always @ (negedge rd or posedge rst) `else always @ (posedge rd or posedge rst) `endif begin if(rst) charreceivedn <= 1'b0; else if(charreceivedp != charreceivedn) charreceivedn <= ~charreceivedn; end ////assign bus = (rd) ? output_buffer : {WORD_LEN{1'bz}}; assign data_out = (rd) ? output_buffer : {WORD_LEN{1'bz}}; //// assign sck = (modeint[1])? ~sckint : sckint; assign mosi = (ss) ? 1'b1:_mosi; assign charreceived = (charreceivedp ^ charreceivedn); endmodule