请高手帮忙用EPLD 模拟Eprom功能（AT24C02）

IO357 · 发表于 2010-1-30 23:29

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折腾了一周一点头绪都没有，想起了论坛上的兄弟姐妹，请大家帮帮忙啊

IO357 · 发表于 2010-2-4 22:51

找到一个I2C Slave的代码，可惜Verlog看不懂，发上来给大家参考

///////////////////////////////////////////////////////////////////////////////
//
//  Alacron Inc. - Confidential: All Rights Reserved
//  Copyright (C) 2003
//
//  Title    : I2C Slave Control Logic
//  File       : I2CSLAVE.v
//  Author    : Gabor Szakacs
//  Created    : 25-May-2004 - Adapted from I2CSLAVE.abl
//
//
///////////////////////////////////////////////////////////////////////////////
//
//  Description :
// This code implements an I2C slave-only controller.
// Access to internal registers uses the sub-address
// protocol like a serial EEPROM.  No registers are
// implemented in this module, however the module
// provides a simple bus interface to external registers.
// GLS - 12/13/00
// I2C inputs are oversampled by clk_in, which should run
// at a minimum of 5 MHz for a 100 KHz I2C bus.  The
// debouncing on the inputs has been tested at up to 80 MHz.
// The I2C 7-bit device address is set by i2c_address.  Address
// 0x6A was selected for FastImage because it doesn't
// conflict with other devices on board.
// Because of limitations in Xilinx Abel, the I/O buffers
// for the I2C SDA and SCL signals were external to this
// macro.
// Three 8-bit buses are implemented for read data, write
// data and subaddress.  For a simple implementation where
// only one 8-bit register is required, the subaddress may
// be used as the register output using simple write and
// read protocol on the I2C bus.  In this case looping the
// subaddress output to the read data bus allows register
// read-back.
// For use with multiple internal registers, the subaddress
// provides the register address.  The rd_wr_out output indicates
// the direction of the current I2C bus transaction and may
// be used to enable read data onto an externally combined
// read/write data bus.  The wr_pulse_out signal can be used as
// an active-high latch enable or clock enable for the
// external registers.  It comes on for one period of clk_in
// and the subaddress and data are valid for at least one
// clk_in period before and after wr_pulse_out.
// A rd_pulse_out output goes high for one clk_in period at the
// beginning of each data byte read.  This indicates the
// time when external data is latched from the read data
// bus.  It may be used to create side-effects on read
// such as clearing sticky status bits.
//
///////////////////////////////////////////////////////////////////////////////
//
//  Modules Instantiated: none
//
///////////////////////////////////////////////////////////////////////////////
//
//  Modification History:
//
//  Added clock enable to slow down state logic with fast input clock
//  6/9/05 - GLS.
//
//
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
`timescale 1 ns / 100 ps
module I2Cslave
(
  sda_io,
  scl_in,
  rd_bus_7_0_in,
  clk_in,
  clr_in,
  subaddr_7_0_out,
  wr_bus_7_0_out,
  wr_pulse_out,
  rd_pulse_out,
  rd_wr_out
);
// Inputs:
// I2C inputs (SDA is I/O externally)
inout sda_io;
input scl_in;
// 8-bit bus for reading registers
input [7:0] rd_bus_7_0_in;
// High-speed clock for state machine logic
input clk_in;
// Asynchronous reset can be grounded for synthesis
input clr_in;
// Outputs:
// 8-bit subaddress for register selection
output [7:0] subaddr_7_0_out;
reg [7:0] subaddr_7_0_out;
// 8-bit bus for writing registers
output [7:0] wr_bus_7_0_out;
reg [7:0] wr_bus_7_0_out;
// I2C data output drive low signal (1 = drive SDA low)
reg drive_sda;
// Register write pulse.  On for one clk_in cycle.
output wr_pulse_out;
reg wr_pulse_out;
// Register read pulse.  On for one clk_in cycle.
output rd_pulse_out;
reg rd_pulse_out;
// Read / not Write.  For external bus drivers if necessary.
output rd_wr_out;
reg rd_wr_out;
// Internal Nodes:
// I2C input debounced nodes:
reg [3:0] sda_sr, scl_sr;
reg sda, scl;
// I2C edge detection nodes:
reg was_sda, was_scl;
// Delayed pulses for address increment:
reg rd_pls_dly, wr_pls_dly;
// I2C protocol state nodes:
reg i2c_start, i2c_stop;
reg [2:0] byte_count;
reg ack_cyc;
reg addr_byte, addr_ack, subad_byte, subad_ack, data_byte;
// Edge detection:
reg was_ack;
reg my_cyc;
// Input data shift register
reg [7:0] in_sr;
// Output data shift register
reg [7:0] out_sr;
// internal node for bidirectional SDA line:
wire sda_in;
IBUF sda_ibuf (.I (sda_io), .O (sda_in));
OBUFE sda_obuf (.I (1'b0), .E (drive_sda), .O (sda_io));
parameter i2c_address = 7'b0110101; // 6A write, 6B read

// Equations
// Debounce, then delay debounced signals for edge detection
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   sda_sr <= 4'b1111;  // Start up assuming quiescent state of inputs
   sda <= 1;
   was_sda <= 0;
   scl_sr <= 4'b1111;  // Start up assuming quiescent state of inputs
   scl <= 1;
   was_scl <= 0;
end
  else
begin
   sda_sr <= {sda_sr[2:0], sda_in};
   if (sda_sr == 4'b0000) sda <= 0;
   else if (sda_sr == 4'b1111) sda <= 1;
   was_sda <= sda;
   scl_sr <= {scl_sr[2:0], scl_in};
   if (scl_sr == 4'b0000) scl <= 0;
   else if (scl_sr == 4'b1111) scl <= 1;
   was_scl <= scl;
end
// Detect start and stop conditions on I2C bus:
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   i2c_start <= 0;
   i2c_stop <= 0;
end
  else
begin
   if (scl & was_scl & !sda & was_sda) i2c_start <= 1; // Falling edge of SDA with SCL high
   else if (!scl & !was_scl) i2c_start <= 0; // Hold until SCL has fallen
   i2c_stop <= scl & was_scl & sda & !was_sda ; // Rising edge of SDA with SCL high
   // i2c_stop is only on for one clock cycle
end
// Increment bit counter on falling edges of the
// SCL signal after the first in a packet.
// Count bit position within bytes:
always @ (posedge clk_in or posedge i2c_start)
  if (i2c_start)
begin
   ack_cyc <= 0;
   byte_count <= 0;
end
  else if (!scl & was_scl & !i2c_start)
begin
   // ack_cyc is really bit 3 of byte_count, counting from 0 to 8
   {ack_cyc,byte_count} <= ack_cyc ? 0 : {ack_cyc,byte_count} + 1;
end
// For edge detection of ack cycles:
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   was_ack <= 0;
end
  else
begin
   was_ack <= ack_cyc;
end
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   addr_byte <= 0;
   addr_ack <= 0;
   subad_byte <= 0;
   subad_ack <= 0;
   wr_pulse_out <= 0;
   rd_pulse_out <= 0;
end
  else
begin
   // addr_byte is on during the first byte transmitted after
   // a START condition.
   if (i2c_start) addr_byte <= 1;
   else if (ack_cyc) addr_byte <= 0;
   // addr_ack is on during acknowledge cycle of the address
   // byte.
   if (addr_byte & ack_cyc) addr_ack <= 1;
   else if (!ack_cyc) addr_ack <= 0;
   // subad_byte is on for the second byte of my write cycle.
   if (addr_ack & !ack_cyc & !rd_wr_out & my_cyc) subad_byte <= 1;
   else if (ack_cyc) subad_byte <= 0;
   // subad_ack is on during the acknowledge cycle of the
   // subaddress byte.
   if (subad_byte & ack_cyc) subad_ack <= 1;
   else if (!ack_cyc) subad_ack <= 0;
   // data_byte is on for my read or write data cycles.  This is
   // any read cycle after the address, or write cycles after
   // the subaddress.  It remains on until the I2C STOP event or
   // any NACK.
   if (addr_ack & !ack_cyc & rd_wr_out & my_cyc | subad_ack & !ack_cyc) data_byte <= 1;
   else if (i2c_stop | ack_cyc & scl & sda) data_byte <= 0;
   // wr_pulse_out is on for one clock cycle while the data
   // on the output bus is valid.
   wr_pulse_out <= data_byte & !ack_cyc & was_ack & !rd_wr_out;
   // rd_pulse_out is on for one clock cycle when external
   // read data is transfered into the output shift register
   // for transmission to the I2C bus.
   rd_pulse_out <= addr_ack & !ack_cyc & rd_wr_out & my_cyc    // First read cycle
            | data_byte & !ack_cyc & was_ack & rd_wr_out ; // Subsequent read cycles
end
// wr_bus_7_0_out is loaded from the I2C input S/R at the
// end of each write data cycle.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   wr_bus_7_0_out <= 0;
end
  else if (data_byte & ack_cyc & !was_ack & !rd_wr_out)
begin
   wr_bus_7_0_out <= in_sr;
end
// out_sr shifts data out to the I2C bus during read
// data cycles.  Transitions occur after the falling
// edge of SCL.  Fills with 1's from right.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   out_sr <= 8'b11111111;
end
  else
begin
   if (rd_pulse_out) out_sr <= rd_bus_7_0_in;
   else if (!scl & was_scl) out_sr <= {out_sr[6:0],1'b1};
end
// Delayed pulses for incrementing subaddress:
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   wr_pls_dly <= 0;
   rd_pls_dly <= 0;
end
  else
begin
   wr_pls_dly <= wr_pulse_out;
   rd_pls_dly <= rd_pulse_out;
end
// subaddr_7_0_out is loaded after the second byte of a write
// cycle has fully shifted in.  It increments after each
// read or write access.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   subaddr_7_0_out <= 0;
end
  else
begin
   if (subad_byte & ack_cyc) subaddr_7_0_out <= in_sr;
   // Leave Out this else clause for simple single register version
   // In this case subaddr_7_0_out becomes the register output and should be
   // wrapped back to rd_bus_7_0_in externally
   else if (wr_pls_dly | rd_pls_dly) subaddr_7_0_out <= subaddr_7_0_out + 1;
end
// Shift I2C data in after rising edge of SCL.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   in_sr <= 0;
end
  else if (scl & !was_scl)
begin
   in_sr <= {in_sr[6:0],sda};
end
// Read / not Write.  For external bus drivers if necessary.
// Latch the Read bit of the address cycle.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   rd_wr_out <= 0;
end
  else if (addr_byte & ack_cyc)
begin
   rd_wr_out <= in_sr[0];
end
// Decode address.  My cycle if address upper 7 bits
// match with i2c_address defined above.
always @ (posedge clk_in or posedge i2c_start)
  if (i2c_start)
begin
end
  else if (addr_byte & ack_cyc)
begin
   my_cyc <= (in_sr[7:1] == i2c_address);
end
// I2C data output drive low signal (1 = drive SDA low)
// Invert this signal for T input of OBUFT or IOBUF
// or use it directly for OBUFE.
always @ (posedge clk_in or posedge clr_in)
  if (clr_in)
begin
   drive_sda <= 0;
end
  else
begin
   drive_sda <= my_cyc & addr_ack    // Address acknowledge
         | my_cyc & !rd_wr_out & ack_cyc // Write byte acknowledge
         | data_byte & rd_wr_out & !ack_cyc & !out_sr[7] ;  // Read Data
end
endmodule // I2Cslave

IO357 · 发表于 2010-2-8 21:42

问题已经解决了，一片7128就实现了。

IO357 · 发表于 2010-2-8 21:44

问题已经解决了，一片7128就实现了。

zxli36 · 发表于 2010-2-10 11:01

谢谢分享，楼主好品质！

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