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/asynchronous_master_spi/trunk/rtl/spi_master.v
0,0 → 1,263
`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(
clk,/* Peripheral clock/not necessary to be core clock, the core clock can be different (input) */
rst,/* Asynchronus reset, is mandatory to provide this signal, active on posedge (input) */
data,/* In/Out data(bidirectional) */
wr,/* Send data, asynchronus with 'clk' , active on posedge or negedge(input) */
rd,/* Read data, , asynchronus with 'clk' , active on posedge or negedge (input) */
buffempty,/* '1' if transmit buffer is empty (output) */
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)*/
sck,/* SPI 'sck' signal (output) */
mosi,/* SPI 'mosi' signal (output) */
miso,/* SPI 'miso' signal (input) */
ss,/* SPI 'ss' signal (if send buffer is maintained full the ss signal will not go high between between transmit chars)(output) */
lsbfirst,/* If '0' msb is send first, if '1' lsb is send first (input) */
mode,/* All four modes is supported (input) */
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) */
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)*/
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) */
);
 
parameter WORD_LEN = 8;
parameter PRESCALLER_SIZE = 8;
 
input clk;
input rst;
inout [WORD_LEN - 1:0]data;
input wr;
input rd;
output buffempty;
input [2:0]prescaller;
output sck;
output mosi;
reg _mosi;
input miso;
output reg ss;
input lsbfirst;
input [1:0]mode;
output reg senderr;
input res_senderr;
output charreceived;
 
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 <= data;
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 ****************/
/***********************************************/
parameter state_idle = 1'b0;
parameter 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(!lsbfirstint)
_mosi <= shift_reg_out[WORD_LEN - 1];
else
_mosi <= shift_reg_out[0];
 
if(sckint[4:1] == WORD_LEN)
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
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 data = (rd) ? output_buffer : {WORD_LEN{1'bz}};
 
assign sck = (modeint[1])? ~sckint : sckint;
assign mosi = (ss) ? 1'b1:_mosi;
assign charreceived = (charreceivedp ^ charreceivedn);
 
endmodule

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