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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 1.14 2009-01-20 10:25:29 rherveille Exp $
//
// $Date: 2009-01-20 10:25:29 $
// $Revision: 1.14 $
// $Author: rherveille $
// $Locker: $
// $State: Exp $
//
// Change History:
// $Log: $
// Revision 1.14 2009/01/20 10:25:29 rherveille
// Added clock synchronization logic
// Fixed slave_wait signal
//
// Revision 1.13 2009/01/19 20:29:26 rherveille
// Fixed synopsys miss spell (synopsis)
// Fixed cr[0] register width
// Fixed ! usage instead of ~
// Fixed bit controller parameter width to 18bits
//
// 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 (
input clk, // system clock
input rst, // synchronous active high reset
input nReset, // asynchronous active low reset
input ena, // core enable signal
input [15:0] clk_cnt, // clock prescale value
input [ 3:0] cmd, // command (from byte controller)
output reg cmd_ack, // command complete acknowledge
output reg busy, // i2c bus busy
output reg al, // i2c bus arbitration lost
input din,
output reg dout,
input scl_i, // i2c clock line input
output scl_o, // i2c clock line output
output reg scl_oen, // i2c clock line output enable (active low)
input sda_i, // i2c data line input
output sda_o, // i2c data line output
output reg sda_oen // i2c data line output enable (active low)
);
//
// variable declarations
//
reg [ 1:0] cSCL, cSDA; // capture SCL and SDA
reg [ 2:0] fSCL, fSDA; // SCL and SDA filter inputs
reg sSCL, sSDA; // filtered and synchronized SCL and SDA inputs
reg dSCL, dSDA; // delayed versions of sSCL and sSDA
reg dscl_oen; // delayed scl_oen
reg sda_chk; // check SDA output (Multi-master arbitration)
reg clk_en; // clock generation signals
reg slave_wait; // slave inserts wait states
reg [15:0] cnt; // clock divider counter (synthesis)
reg [13:0] filter_cnt; // clock divider for filter
// state machine variable
reg [17:0] 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 <= scl_oen;
// slave_wait is asserted when master wants to drive SCL high, but the slave pulls it low
// slave_wait remains asserted until the slave releases SCL
always @(posedge clk or negedge nReset)
if (!nReset) slave_wait <= 1'b0;
else slave_wait <= (scl_oen & ~dscl_oen & ~sSCL) | (slave_wait & ~sSCL);
// master drives SCL high, but another master pulls it low
// master start counting down its low cycle now (clock synchronization)
wire scl_sync = dSCL & ~sSCL & scl_oen;
// generate clk enable signal
always @(posedge clk or negedge nReset)
if (~nReset)
begin
cnt <= 16'h0;
clk_en <= 1'b1;
end
else if (rst || ~|cnt || !ena || scl_sync)
begin
cnt <= clk_cnt;
clk_en <= 1'b1;
end
else if (slave_wait)
begin
cnt <= cnt;
clk_en <= 1'b0;
end
else
begin
cnt <= cnt - 16'h1;
clk_en <= 1'b0;
end
// generate bus status controller
// capture SDA and SCL
// reduce metastability risk
always @(posedge clk or negedge nReset)
if (!nReset)
begin
cSCL <= 2'b00;
cSDA <= 2'b00;
end
else if (rst)
begin
cSCL <= 2'b00;
cSDA <= 2'b00;
end
else
begin
cSCL <= {cSCL[0],scl_i};
cSDA <= {cSDA[0],sda_i};
end
// filter SCL and SDA signals; (attempt to) remove glitches
always @(posedge clk or negedge nReset)
if (!nReset ) filter_cnt <= 14'h0;
else if (rst || !ena ) filter_cnt <= 14'h0;
else if (~|filter_cnt) filter_cnt <= clk_cnt[15:2]; //16x I2C bus frequency
else filter_cnt <= filter_cnt -1;
always @(posedge clk or negedge nReset)
if (!nReset)
begin
fSCL <= 3'b111;
fSDA <= 3'b111;
end
else if (rst)
begin
fSCL <= 3'b111;
fSDA <= 3'b111;
end
else if (~|filter_cnt)
begin
fSCL <= {fSCL[1:0],cSCL[1]};
fSDA <= {fSDA[1:0],cSDA[1]};
end
// generate filtered SCL and SDA signals
always @(posedge clk or negedge nReset)
if (~nReset)
begin
sSCL <= 1'b1;
sSDA <= 1'b1;
dSCL <= 1'b1;
dSDA <= 1'b1;
end
else if (rst)
begin
sSCL <= 1'b1;
sSDA <= 1'b1;
dSCL <= 1'b1;
dSDA <= 1'b1;
end
else
begin
sSCL <= &fSCL[2:1] | &fSCL[1:0] | (fSCL[2] & fSCL[0]);
sSDA <= &fSDA[2:1] | &fSDA[1:0] | (fSDA[2] & fSDA[0]);
dSCL <= sSCL;
dSDA <= 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
reg sta_condition;
reg sto_condition;
always @(posedge clk or negedge nReset)
if (~nReset)
begin
sta_condition <= 1'b0;
sto_condition <= 1'b0;
end
else if (rst)
begin
sta_condition <= 1'b0;
sto_condition <= 1'b0;
end
else
begin
sta_condition <= ~sSDA & dSDA & sSCL;
sto_condition <= sSDA & ~dSDA & sSCL;
end
// generate i2c bus busy signal
always @(posedge clk or negedge nReset)
if (!nReset) busy <= 1'b0;
else if (rst ) busy <= 1'b0;
else busy <= (sta_condition | busy) & ~sto_condition;
// generate arbitration lost signal
// aribitration lost when:
// 1) master drives SDA high, but the i2c bus is low
// 2) stop detected while not requested
reg cmd_stop;
always @(posedge clk or negedge nReset)
if (~nReset)
cmd_stop <= 1'b0;
else if (rst)
cmd_stop <= 1'b0;
else if (clk_en)
cmd_stop <= cmd == `I2C_CMD_STOP;
always @(posedge clk or negedge nReset)
if (~nReset)
al <= 1'b0;
else if (rst)
al <= 1'b0;
else
al <= (sda_chk & ~sSDA & sda_oen) | (|c_state & sto_condition & ~cmd_stop);
// generate dout signal (store SDA on rising edge of SCL)
always @(posedge clk)
if (sSCL & ~dSCL) dout <= sSDA;
// generate statemachine
// nxt_state decoder
parameter [17:0] idle = 18'b0_0000_0000_0000_0000;
parameter [17:0] start_a = 18'b0_0000_0000_0000_0001;
parameter [17:0] start_b = 18'b0_0000_0000_0000_0010;
parameter [17:0] start_c = 18'b0_0000_0000_0000_0100;
parameter [17:0] start_d = 18'b0_0000_0000_0000_1000;
parameter [17:0] start_e = 18'b0_0000_0000_0001_0000;
parameter [17:0] stop_a = 18'b0_0000_0000_0010_0000;
parameter [17:0] stop_b = 18'b0_0000_0000_0100_0000;
parameter [17:0] stop_c = 18'b0_0000_0000_1000_0000;
parameter [17:0] stop_d = 18'b0_0000_0001_0000_0000;
parameter [17:0] rd_a = 18'b0_0000_0010_0000_0000;
parameter [17:0] rd_b = 18'b0_0000_0100_0000_0000;
parameter [17:0] rd_c = 18'b0_0000_1000_0000_0000;
parameter [17:0] rd_d = 18'b0_0001_0000_0000_0000;
parameter [17:0] wr_a = 18'b0_0010_0000_0000_0000;
parameter [17:0] wr_b = 18'b0_0100_0000_0000_0000;
parameter [17:0] wr_c = 18'b0_1000_0000_0000_0000;
parameter [17:0] wr_d = 18'b1_0000_0000_0000_0000;
always @(posedge clk or negedge nReset)
if (!nReset)
begin
c_state <= idle;
cmd_ack <= 1'b0;
scl_oen <= 1'b1;
sda_oen <= 1'b1;
sda_chk <= 1'b0;
end
else if (rst | al)
begin
c_state <= idle;
cmd_ack <= 1'b0;
scl_oen <= 1'b1;
sda_oen <= 1'b1;
sda_chk <= 1'b0;
end
else
begin
cmd_ack <= 1'b0; // default no command acknowledge + assert cmd_ack only 1clk cycle
if (clk_en)
case (c_state) // synopsys full_case parallel_case
// idle state
idle:
begin
case (cmd) // synopsys full_case parallel_case
`I2C_CMD_START: c_state <= start_a;
`I2C_CMD_STOP: c_state <= stop_a;
`I2C_CMD_WRITE: c_state <= wr_a;
`I2C_CMD_READ: c_state <= rd_a;
default: c_state <= idle;
endcase
scl_oen <= scl_oen; // keep SCL in same state
sda_oen <= sda_oen; // keep SDA in same state
sda_chk <= 1'b0; // don't check SDA output
end
// start
start_a:
begin
c_state <= start_b;
scl_oen <= scl_oen; // keep SCL in same state
sda_oen <= 1'b1; // set SDA high
sda_chk <= 1'b0; // don't check SDA output
end
start_b:
begin
c_state <= start_c;
scl_oen <= 1'b1; // set SCL high
sda_oen <= 1'b1; // keep SDA high
sda_chk <= 1'b0; // don't check SDA output
end
start_c:
begin
c_state <= start_d;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= 1'b0; // set SDA low
sda_chk <= 1'b0; // don't check SDA output
end
start_d:
begin
c_state <= start_e;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= 1'b0; // keep SDA low
sda_chk <= 1'b0; // don't check SDA output
end
start_e:
begin
c_state <= idle;
cmd_ack <= 1'b1;
scl_oen <= 1'b0; // set SCL low
sda_oen <= 1'b0; // keep SDA low
sda_chk <= 1'b0; // don't check SDA output
end
// stop
stop_a:
begin
c_state <= stop_b;
scl_oen <= 1'b0; // keep SCL low
sda_oen <= 1'b0; // set SDA low
sda_chk <= 1'b0; // don't check SDA output
end
stop_b:
begin
c_state <= stop_c;
scl_oen <= 1'b1; // set SCL high
sda_oen <= 1'b0; // keep SDA low
sda_chk <= 1'b0; // don't check SDA output
end
stop_c:
begin
c_state <= stop_d;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= 1'b0; // keep SDA low
sda_chk <= 1'b0; // don't check SDA output
end
stop_d:
begin
c_state <= idle;
cmd_ack <= 1'b1;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= 1'b1; // set SDA high
sda_chk <= 1'b0; // don't check SDA output
end
// read
rd_a:
begin
c_state <= rd_b;
scl_oen <= 1'b0; // keep SCL low
sda_oen <= 1'b1; // tri-state SDA
sda_chk <= 1'b0; // don't check SDA output
end
rd_b:
begin
c_state <= rd_c;
scl_oen <= 1'b1; // set SCL high
sda_oen <= 1'b1; // keep SDA tri-stated
sda_chk <= 1'b0; // don't check SDA output
end
rd_c:
begin
c_state <= rd_d;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= 1'b1; // keep SDA tri-stated
sda_chk <= 1'b0; // don't check SDA output
end
rd_d:
begin
c_state <= idle;
cmd_ack <= 1'b1;
scl_oen <= 1'b0; // set SCL low
sda_oen <= 1'b1; // keep SDA tri-stated
sda_chk <= 1'b0; // don't check SDA output
end
// write
wr_a:
begin
c_state <= wr_b;
scl_oen <= 1'b0; // keep SCL low
sda_oen <= din; // set SDA
sda_chk <= 1'b0; // don't check SDA output (SCL low)
end
wr_b:
begin
c_state <= wr_c;
scl_oen <= 1'b1; // set SCL high
sda_oen <= din; // keep SDA
sda_chk <= 1'b0; // don't check SDA output yet
// allow some time for SDA and SCL to settle
end
wr_c:
begin
c_state <= wr_d;
scl_oen <= 1'b1; // keep SCL high
sda_oen <= din;
sda_chk <= 1'b1; // check SDA output
end
wr_d:
begin
c_state <= idle;
cmd_ack <= 1'b1;
scl_oen <= 1'b0; // set SCL low
sda_oen <= din;
sda_chk <= 1'b0; // don't check SDA output (SCL low)
end
endcase
end
// assign scl and sda output (always gnd)
assign scl_o = 1'b0;
assign sda_o = 1'b0;
endmodule