I2C Verilog的实现（一）

<span style="font-size:14px;">`timescale 1ns / 1ps
module test(
sda
);

    reg scl;
    inout sda;
    reg sda_out;
    wire    sda_in;
    reg [7:0]   data;

    reg start_flag, stop_flag;

    assign sda = sda_out ? 1'bz : 1'b0;
    assign sda_in = sda;
    pullup( sda );


    I2CTEST testmine(.SDA(sda), .SCL(scl));

    initial
        begin
           scl = 0;
            sda_out = 0;
            data = 8'h27;
            start_flag = 0;
            #160000;
            start ( );
        end

    always
    begin
       #50000 scl = ~scl;
   end

    always @ (posedge start_flag)
    begin
       repeat (8)
          begin
             wait ( scl == 0 );
                #20000;
                sda_out = data[7];
                #40000;
                data = data << 1;
            end
            wait (~ scl);
            #20000;
            sda_out = 1;
            #160000;
            stop ( );
    end

    always @ ( posedge stop_flag)
    begin
//     sda_out = 0;
//     #50000;
       sda_out = 1;
    end


    task start;
    begin
        wait (scl == 0);
        #20000;
        sda_out = 1;
        wait ( scl == 1 );
        #20000;
        sda_out = 0;
        start_flag = 1;
    end
    endtask

    task stop;
    begin
        wait ( scl == 0 );
        #20000;
        sda_out = 0;
        wait ( scl ==1 );
        #20000;
        sda_out = 1;
        stop_flag = 1;
        end
    endtask

endmodule</span>

I2C程序

<span style="font-family:Arial;">`timescale 1ns / 1ps
module I2CTEST(
SDA, SCL
);

input SCL;
inout SDA;

// The 7-bits address that we want for our I2C slave
parameter I2C_ADR = 7'h13;

//---------------------------------------------
//start,stop condition judgement
//---------------------------------------------
wire start, stop;
reg sda1, sda2;
reg sda11;

always @ ( posedge SCL )
sda1 <= SDA;

always @ ( negedge SCL )
sda2 <= SDA;

always @ ( negedge SCL )
sda11 <= sda1;


assign start = sda11 & (!sda2);
assign stop = sda2 & ( !sda11 );


//----------------------------------------------
//count setting
//----------------------------------------------
reg [3:0]  bitcont;
wire bit_ack = bitcont[3];

always @ ( posedge SCL or posedge start)
begin
    if ( start )
    bitcont <=  4'h6;
    else
    begin
        if (bit_ack)
        bitcont <= 4'h6;
        else
        bitcont <= bitcont -4'h1;
    end
end



//-------------------------------------
//get sda using posedge scl
//-------------------------------------

reg sdar;

always @ ( posedge SCL ) sdar <= SDA;

//----------------------------------------
//address match
//----------------------------------------

reg addr_match, op_read;

always @ ( negedge SCL or posedge start )
begin
    if ( start )
    begin
        addr_match <= 1'h1;
        op_read <= 1'h0;
    end
    else
    begin
        if( (bitcont == 6) & (sdar != I2C_ADR[6])) addr_match <= 1'h0;
        if( (bitcont == 5) & (sdar != I2C_ADR[5])) addr_match <= 1'h0;
        if( (bitcont == 4) & (sdar != I2C_ADR[4])) addr_match <= 1'h0;
        if( (bitcont == 3) & (sdar != I2C_ADR[3])) addr_match <= 1'h0;
        if( (bitcont == 2) & (sdar != I2C_ADR[2])) addr_match <= 1'h0;
        if( (bitcont == 1) & (sdar != I2C_ADR[1])) addr_match <= 1'h0;
        if( (bitcont == 0) & (sdar != I2C_ADR[0])) addr_match <= 1'h0;
        if( bitcont == 0 ) op_read <= sdar;
    end
end

//-----------------------------------------------------------------------
//send ack
//-----------------------------------------------------------------------

reg ack_assert;

always @ ( negedge SCL )
begin
    if ( bit_ack & addr_match & op_read )
    ack_assert <= 1'h1;
    else
    ack_assert <= 1'h0;
end

//-------------------------------------------------------------------------
//control SDA line
//-------------------------------------------------------------------------

assign SDA = ack_assert ? 1'h0 : 1'hz;
pullup ( SDA );

endmodule