?? i2c_master_bit_ctrl.v.txt
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/////////////////////////////////////////////////////////////////////
//// ////
//// WISHBONE rev.B2 compliant I2C Master bit-controller ////
//// ////
//// ////
//// Author: Richard Herveille ////
//// richard@asics.ws ////
//// www.asics.ws ////
//// ////
//// Downloaded from: http://www.opencores.org/projects/i2c/ ////
//// ////
/////////////////////////////////////////////////////////////////////
//// ////
//// Copyright (C) 2001 Richard Herveille ////
//// richard@asics.ws ////
//// ////
//// This source file may be used and distributed without ////
//// restriction provided that this copyright statement is not ////
//// removed from the file and that any derivative work contains ////
//// the original copyright notice and the associated disclaimer.////
//// ////
//// THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY ////
//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED ////
//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ////
//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR ////
//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ////
//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ////
//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE ////
//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR ////
//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF ////
//// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ////
//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT ////
//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ////
//// POSSIBILITY OF SUCH DAMAGE. ////
//// ////
/////////////////////////////////////////////////////////////////////
// CVS Log
//
// $Id: i2c_master_bit_ctrl.v,v 1.12 2006/09/04 09:08:13 rherveille Exp $
//
// $Date: 2006/09/04 09:08:13 $
// $Revision: 1.12 $
// $Author: rherveille $
// $Locker: $
// $State: Exp $
//
// Change History:
// $Log: i2c_master_bit_ctrl.v,v $
// Revision 1.12 2006/09/04 09:08:13 rherveille
// fixed short scl high pulse after clock stretch
// fixed slave model not returning correct '(n)ack' signal
//
// Revision 1.11 2004/05/07 11:02:26 rherveille
// Fixed a bug where the core would signal an arbitration lost (AL bit set), when another master controls the bus and the other master generates a STOP bit.
//
// Revision 1.10 2003/08/09 07:01:33 rherveille
// Fixed a bug in the Arbitration Lost generation caused by delay on the (external) sda line.
// Fixed a potential bug in the byte controller's host-acknowledge generation.
//
// Revision 1.9 2003/03/10 14:26:37 rherveille
// Fixed cmd_ack generation item (no bug).
//
// Revision 1.8 2003/02/05 00:06:10 rherveille
// Fixed a bug where the core would trigger an erroneous 'arbitration lost' interrupt after being reset, when the reset pulse width < 3 clk cycles.
//
// Revision 1.7 2002/12/26 16:05:12 rherveille
// Small code simplifications
//
// Revision 1.6 2002/12/26 15:02:32 rherveille
// Core is now a Multimaster I2C controller
//
// Revision 1.5 2002/11/30 22:24:40 rherveille
// Cleaned up code
//
// Revision 1.4 2002/10/30 18:10:07 rherveille
// Fixed some reported minor start/stop generation timing issuess.
//
// Revision 1.3 2002/06/15 07:37:03 rherveille
// Fixed a small timing bug in the bit controller.\nAdded verilog simulation environment.
//
// Revision 1.2 2001/11/05 11:59:25 rherveille
// Fixed wb_ack_o generation bug.
// Fixed bug in the byte_controller statemachine.
// Added headers.
//
//
/////////////////////////////////////
// Bit controller section
/////////////////////////////////////
//
// Translate simple commands into SCL/SDA transitions
// Each command has 5 states, A/B/C/D/idle
//
// start: SCL ~~~~~~~~~~\____
// SDA ~~~~~~~~\______
// x | A | B | C | D | i
//
// repstart SCL ____/~~~~\___
// SDA __/~~~\______
// x | A | B | C | D | i
//
// stop SCL ____/~~~~~~~~
// SDA ==\____/~~~~~
// x | A | B | C | D | i
//
//- write SCL ____/~~~~\____
// SDA ==X=========X=
// x | A | B | C | D | i
//
//- read SCL ____/~~~~\____
// SDA XXXX=====XXXX
// x | A | B | C | D | i
//
// Timing: Normal mode Fast mode
///////////////////////////////////////////////////////////////////////
// Fscl 100KHz 400KHz
// Th_scl 4.0us 0.6us High period of SCL
// Tl_scl 4.7us 1.3us Low period of SCL
// Tsu:sta 4.7us 0.6us setup time for a repeated start condition
// Tsu:sto 4.0us 0.6us setup time for a stop conditon
// Tbuf 4.7us 1.3us Bus free time between a stop and start condition
//
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "i2c_master_defines.v"
module i2c_master_bit_ctrl(
clk, rst, nReset,
clk_cnt, ena, cmd, cmd_ack, busy, al, din, dout,
scl_i, scl_o, scl_oen, sda_i, sda_o, sda_oen
);
//
// inputs & outputs
//
input clk;
input rst;
input nReset;
input ena; // core enable signal
input [15:0] clk_cnt; // clock prescale value
input [3:0] cmd;
output cmd_ack; // command complete acknowledge
reg cmd_ack;
output busy; // i2c bus busy
reg busy;
output al; // i2c bus arbitration lost
reg al;
input din;
output dout;
reg dout;
// I2C lines
input scl_i; // i2c clock line input
output scl_o; // i2c clock line output
output scl_oen; // i2c clock line output enable (active low)
reg scl_oen;
input sda_i; // i2c data line input
output sda_o; // i2c data line output
output sda_oen; // i2c data line output enable (active low)
reg sda_oen;
//
// variable declarations
//
reg sSCL, sSDA; // synchronized SCL and SDA inputs
reg dscl_oen; // delayed scl_oen
reg sda_chk; // check SDA output (Multi-master arbitration)
reg clk_en; // clock generation signals
wire slave_wait;
// reg [15:0] cnt = clk_cnt; // clock divider counter (simulation)
reg [15:0] cnt; // clock divider counter (synthesis)
// state machine variable
reg [16:0] c_state; // synopsys enum_state
//
// module body
//
// whenever the slave is not ready it can delay the cycle by pulling SCL low
// delay scl_oen
always @(posedge clk)
dscl_oen <= #1 scl_oen;
assign slave_wait = dscl_oen && !sSCL;
// generate clk enable signal
always @(posedge clk or negedge nReset)
if(~nReset)
begin
cnt <= #1 16'h0;
clk_en <= #1 1'b1;
end
else if (rst)
begin
cnt <= #1 16'h0;
clk_en <= #1 1'b1;
end
else if ( ~|cnt || !ena)
begin
cnt <= #1 clk_cnt;
clk_en <= #1 1'b1;
end
else if (slave_wait)
begin
cnt <= #1 cnt;
clk_en <= #1 1'b0;
end
else
begin
cnt <= #1 cnt - 16'h1;
clk_en <= #1 1'b0;
end
// generate bus status controller
reg dSCL, dSDA;
reg sta_condition;
reg sto_condition;
// synchronize SCL and SDA inputs
// reduce metastability risc
always @(posedge clk or negedge nReset)
if (~nReset)
begin
sSCL <= #1 1'b1;
sSDA <= #1 1'b1;
dSCL <= #1 1'b1;
dSDA <= #1 1'b1;
end
else if (rst)
begin
sSCL <= #1 1'b1;
sSDA <= #1 1'b1;
dSCL <= #1 1'b1;
dSDA <= #1 1'b1;
end
else
begin
sSCL <= #1 scl_i;
sSDA <= #1 sda_i;
dSCL <= #1 sSCL;
dSDA <= #1 sSDA;
end
// detect start condition => detect falling edge on SDA while SCL is high
// detect stop condition => detect rising edge on SDA while SCL is high
always @(posedge clk or negedge nReset)
if (~nReset)
begin
sta_condition <= #1 1'b0;
sto_condition <= #1 1'b0;
end
else if (rst)
begin
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