Ok, I'm banging my head against the wall with this
I2C core, so I had to post for help. I'm not trying to even look at the SCL/SDA lines right now, just trying to read from some of the registers that have R/W attributes. When I read all of the registers after reset, I am seeing $00. It seems to ignore all writes, except to register 1. The, whatever value I write to register 1, I am reading from all registers 0 thru 7. Sounds like memory decoding issue, but I am sure I have it correct as I am using the same design to decode PS2 and TFT chip selects... Can anyone help? This is the top level code:
Code: Select all
/////////////////////////////////////////////////////////////////////
//// ////
//// WISHBONE revB.2 compliant I2C Master controller Top-level ////
//// ////
//// ////
//// 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_top.v,v 1.12 2009-01-19 20:29:26 rherveille Exp $
//
// $Date: 2009-01-19 20:29:26 $
// $Revision: 1.12 $
// $Author: rherveille $
// $Locker: $
// $State: Exp $
//
// Change History:
// Revision 1.11 2005/02/27 09:26:24 rherveille
// Fixed register overwrite issue.
// Removed full_case pragma, replaced it by a default statement.
//
// Revision 1.10 2003/09/01 10:34:38 rherveille
// Fix a blocking vs. non-blocking error in the wb_dat output mux.
//
// Revision 1.9 2003/01/09 16:44:45 rherveille
// Fixed a bug in the Command Register declaration.
//
// Revision 1.8 2002/12/26 16:05:12 rherveille
// Small code simplifications
//
// Revision 1.7 2002/12/26 15:02:32 rherveille
// Core is now a Multimaster I2C controller
//
// Revision 1.6 2002/11/30 22:24:40 rherveille
// Cleaned up code
//
// Revision 1.5 2001/11/10 10:52:55 rherveille
// Changed PRER reset value from 0x0000 to 0xffff, conform specs.
//
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "i2c_master_defines.v"
module i2c_master_top(
wb_clk_i, wb_rst_i, arst_i, wb_adr_i, wb_dat_i, wb_dat_o,
wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o, wb_inta_o,
scl_pad_i, scl_pad_o, scl_padoen_o, sda_pad_i, sda_pad_o, sda_padoen_o );
// parameters
parameter ARST_LVL = 1'b0; // asynchronous reset level
//
// inputs & outputs
//
// wishbone signals
input wb_clk_i; // master clock input
input wb_rst_i; // synchronous active high reset
input arst_i; // asynchronous reset
input [2:0] wb_adr_i; // lower address bits
input [7:0] wb_dat_i; // databus input
output [7:0] wb_dat_o; // databus output
input wb_we_i; // write enable input
input wb_stb_i; // stobe/core select signal
input wb_cyc_i; // valid bus cycle input
output wb_ack_o; // bus cycle acknowledge output
output wb_inta_o; // interrupt request signal output
reg [7:0] wb_dat_o;
reg wb_ack_o;
reg wb_inta_o;
// I2C signals
// i2c clock line
input scl_pad_i; // SCL-line input
output scl_pad_o; // SCL-line output (always 1'b0)
output scl_padoen_o; // SCL-line output enable (active low)
// i2c data line
input sda_pad_i; // SDA-line input
output sda_pad_o; // SDA-line output (always 1'b0)
output sda_padoen_o; // SDA-line output enable (active low)
//
// variable declarations
//
// registers
reg [15:0] prer; // clock prescale register
reg [ 7:0] ctr; // control register
reg [ 7:0] txr; // transmit register
wire [ 7:0] rxr; // receive register
reg [ 7:0] cr; // command register
wire [ 7:0] sr; // status register
// done signal: command completed, clear command register
wire done;
// core enable signal
wire core_en;
wire ien;
// status register signals
wire irxack;
reg rxack; // received aknowledge from slave
reg tip; // transfer in progress
reg irq_flag; // interrupt pending flag
wire i2c_busy; // bus busy (start signal detected)
wire i2c_al; // i2c bus arbitration lost
reg al; // status register arbitration lost bit
//
// module body
//
// generate internal reset
wire rst_i = arst_i ^ ARST_LVL;
// generate wishbone signals
wire wb_wacc = wb_we_i & wb_ack_o;
// generate acknowledge output signal
always @(posedge wb_clk_i)
wb_ack_o <= #1 wb_cyc_i & wb_stb_i & ~wb_ack_o; // because timing is always honored
// assign DAT_O
always @(posedge wb_clk_i)
begin
case (wb_adr_i) // synopsys parallel_case
3'b000: wb_dat_o <= #1 prer[ 7:0];
3'b001: wb_dat_o <= #1 prer[15:8];
3'b010: wb_dat_o <= #1 ctr;
3'b011: wb_dat_o <= #1 rxr; // write is transmit register (txr)
3'b100: wb_dat_o <= #1 sr; // write is command register (cr)
3'b101: wb_dat_o <= #1 txr;
3'b110: wb_dat_o <= #1 cr;
3'b111: wb_dat_o <= #1 0; // reserved
endcase
end
// generate registers
always @(posedge wb_clk_i or negedge rst_i)
if (!rst_i)
begin
prer <= #1 16'hffff;
ctr <= #1 8'h0;
txr <= #1 8'h0;
end
else if (wb_rst_i)
begin
prer <= #1 16'hffff;
ctr <= #1 8'h0;
txr <= #1 8'h0;
end
else
if (wb_wacc)
case (wb_adr_i) // synopsys parallel_case
3'b000 : prer [ 7:0] <= #1 wb_dat_i;
3'b001 : prer [15:8] <= #1 wb_dat_i;
3'b010 : ctr <= #1 wb_dat_i;
3'b011 : txr <= #1 wb_dat_i;
default: ;
endcase
// generate command register (special case)
always @(posedge wb_clk_i or negedge rst_i)
if (!rst_i)
cr <= #1 8'h0;
else if (wb_rst_i)
cr <= #1 8'h0;
else if (wb_wacc)
begin
if (core_en & (wb_adr_i == 3'b100) )
cr <= #1 wb_dat_i;
end
else
begin
if (done | i2c_al)
cr[7:4] <= #1 4'h0; // clear command bits when done
// or when aribitration lost
cr[2:1] <= #1 2'b0; // reserved bits
cr[0] <= #1 1'b0; // clear IRQ_ACK bit
end
// decode command register
wire sta = cr[7];
wire sto = cr[6];
wire rd = cr[5];
wire wr = cr[4];
wire ack = cr[3];
wire iack = cr[0];
// decode control register
assign core_en = ctr[7];
assign ien = ctr[6];
// hookup byte controller block
i2c_master_byte_ctrl byte_controller (
.clk ( wb_clk_i ),
.rst ( wb_rst_i ),
.nReset ( rst_i ),
.ena ( core_en ),
.clk_cnt ( prer ),
.start ( sta ),
.stop ( sto ),
.read ( rd ),
.write ( wr ),
.ack_in ( ack ),
.din ( txr ),
.cmd_ack ( done ),
.ack_out ( irxack ),
.dout ( rxr ),
.i2c_busy ( i2c_busy ),
.i2c_al ( i2c_al ),
.scl_i ( scl_pad_i ),
.scl_o ( scl_pad_o ),
.scl_oen ( scl_padoen_o ),
.sda_i ( sda_pad_i ),
.sda_o ( sda_pad_o ),
.sda_oen ( sda_padoen_o )
);
// status register block + interrupt request signal
always @(posedge wb_clk_i or negedge rst_i)
if (!rst_i)
begin
al <= #1 1'b0;
rxack <= #1 1'b0;
tip <= #1 1'b0;
irq_flag <= #1 1'b0;
end
else if (wb_rst_i)
begin
al <= #1 1'b0;
rxack <= #1 1'b0;
tip <= #1 1'b0;
irq_flag <= #1 1'b0;
end
else
begin
al <= #1 i2c_al | (al & ~sta);
rxack <= #1 irxack;
tip <= #1 (rd | wr);
irq_flag <= #1 (done | i2c_al | irq_flag) & ~iack; // interrupt request flag is always generated
end
// generate interrupt request signals
always @(posedge wb_clk_i or negedge rst_i)
if (!rst_i)
wb_inta_o <= #1 1'b0;
else if (wb_rst_i)
wb_inta_o <= #1 1'b0;
else
wb_inta_o <= #1 irq_flag && ien; // interrupt signal is only generated when IEN (interrupt enable bit is set)
// assign status register bits
assign sr[7] = rxack;
assign sr[6] = i2c_busy;
assign sr[5] = al;
assign sr[4:2] = 3'h0; // reserved
assign sr[1] = tip;
assign sr[0] = irq_flag;
endmodule
