---------------------------------------------------------------------
|
---------------------------------------------------------------------
|
---- ----
|
---- ----
|
---- WISHBONE revB2 I2C Master Core; bit-controller ----
|
---- WISHBONE revB2 I2C Master Core; bit-controller ----
|
---- ----
|
---- ----
|
---- ----
|
---- ----
|
---- Author: Richard Herveille ----
|
---- Author: Richard Herveille ----
|
---- richard@asics.ws ----
|
---- richard@asics.ws ----
|
---- www.asics.ws ----
|
---- www.asics.ws ----
|
---- ----
|
---- ----
|
---- Downloaded from: http://www.opencores.org/projects/i2c/ ----
|
---- Downloaded from: http://www.opencores.org/projects/i2c/ ----
|
---- ----
|
---- ----
|
---------------------------------------------------------------------
|
---------------------------------------------------------------------
|
---- ----
|
---- ----
|
---- Copyright (C) 2000 Richard Herveille ----
|
---- Copyright (C) 2000 Richard Herveille ----
|
---- richard@asics.ws ----
|
---- richard@asics.ws ----
|
---- ----
|
---- ----
|
---- This source file may be used and distributed without ----
|
---- This source file may be used and distributed without ----
|
---- restriction provided that this copyright statement is not ----
|
---- restriction provided that this copyright statement is not ----
|
---- removed from the file and that any derivative work contains ----
|
---- removed from the file and that any derivative work contains ----
|
---- the original copyright notice and the associated disclaimer.----
|
---- the original copyright notice and the associated disclaimer.----
|
---- ----
|
---- ----
|
---- THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY ----
|
---- THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY ----
|
---- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED ----
|
---- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED ----
|
---- TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ----
|
---- TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ----
|
---- FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR ----
|
---- FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR ----
|
---- OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ----
|
---- OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ----
|
---- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ----
|
---- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ----
|
---- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE ----
|
---- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE ----
|
---- GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR ----
|
---- GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR ----
|
---- BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF ----
|
---- BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF ----
|
---- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ----
|
---- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ----
|
---- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT ----
|
---- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT ----
|
---- OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ----
|
---- OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ----
|
---- POSSIBILITY OF SUCH DAMAGE. ----
|
---- POSSIBILITY OF SUCH DAMAGE. ----
|
---- ----
|
---- ----
|
---------------------------------------------------------------------
|
---------------------------------------------------------------------
|
|
|
-- CVS Log
|
-- CVS Log
|
--
|
--
|
-- $Id: i2c_master_bit_ctrl.vhd,v 1.4 2002-11-30 22:24:37 rherveille Exp $
|
-- $Id: i2c_master_bit_ctrl.vhd,v 1.5 2002-12-26 16:05:47 rherveille Exp $
|
--
|
--
|
-- $Date: 2002-11-30 22:24:37 $
|
-- $Date: 2002-12-26 16:05:47 $
|
-- $Revision: 1.4 $
|
-- $Revision: 1.5 $
|
-- $Author: rherveille $
|
-- $Author: rherveille $
|
-- $Locker: $
|
-- $Locker: $
|
-- $State: Exp $
|
-- $State: Exp $
|
--
|
--
|
-- Change History:
|
-- Change History:
|
-- $Log: not supported by cvs2svn $
|
-- $Log: not supported by cvs2svn $
|
|
-- Revision 1.4 2002/11/30 22:24:37 rherveille
|
|
-- Cleaned up code
|
|
--
|
-- Revision 1.3 2002/10/30 18:09:53 rherveille
|
-- Revision 1.3 2002/10/30 18:09:53 rherveille
|
-- Fixed some reported minor start/stop generation timing issuess.
|
-- Fixed some reported minor start/stop generation timing issuess.
|
--
|
--
|
-- Revision 1.2 2002/06/15 07:37:04 rherveille
|
-- Revision 1.2 2002/06/15 07:37:04 rherveille
|
-- Fixed a small timing bug in the bit controller.\nAdded verilog simulation environment.
|
-- Fixed a small timing bug in the bit controller.\nAdded verilog simulation environment.
|
--
|
--
|
-- Revision 1.1 2001/11/05 12:02:33 rherveille
|
-- Revision 1.1 2001/11/05 12:02:33 rherveille
|
-- Split i2c_master_core.vhd into separate files for each entity; same layout as verilog version.
|
-- Split i2c_master_core.vhd into separate files for each entity; same layout as verilog version.
|
-- Code updated, is now up-to-date to doc. rev.0.4.
|
-- Code updated, is now up-to-date to doc. rev.0.4.
|
-- Added headers.
|
-- Added headers.
|
--
|
--
|
|
|
|
|
--
|
--
|
-------------------------------------
|
-------------------------------------
|
-- Bit controller section
|
-- Bit controller section
|
------------------------------------
|
------------------------------------
|
--
|
--
|
-- Translate simple commands into SCL/SDA transitions
|
-- Translate simple commands into SCL/SDA transitions
|
-- Each command has 5 states, A/B/C/D/idle
|
-- Each command has 5 states, A/B/C/D/idle
|
--
|
--
|
-- start: SCL ~~~~~~~~~~\____
|
-- start: SCL ~~~~~~~~~~~~~~\____
|
-- SDA ~~~~~~~~\______
|
-- SDA XX/~~~~~~~\______
|
-- x | A | B | C | D | i
|
-- x | A | B | C | D | i
|
--
|
--
|
-- repstart SCL ____/~~~~\___
|
-- repstart SCL ______/~~~~~~~\___
|
-- SDA __/~~~\______
|
-- SDA __/~~~~~~~\______
|
-- x | A | B | C | D | i
|
-- x | A | B | C | D | i
|
--
|
--
|
-- stop SCL ____/~~~~~~~~
|
-- stop SCL _______/~~~~~~~~~~~
|
-- SDA ==\____/~~~~~
|
-- SDA ==\___________/~~~~~
|
-- x | A | B | C | D | i
|
-- x | A | B | C | D | i
|
--
|
--
|
--- write SCL ____/~~~~\____
|
--- write SCL ______/~~~~~~~\____
|
-- SDA ==X=========X=
|
-- SDA XXX===============XX
|
-- x | A | B | C | D | i
|
-- x | A | B | C | D | i
|
--
|
--
|
--- read SCL ____/~~~~\____
|
--- read SCL ______/~~~~~~~\____
|
-- SDA XXXX=====XXXX
|
-- SDA XXXXXXX=XXXXXXXXXXX
|
-- x | A | B | C | D | i
|
-- x | A | B | C | D | i
|
--
|
--
|
|
|
-- Timing: Normal mode Fast mode
|
-- Timing: Normal mode Fast mode
|
-----------------------------------------------------------------
|
-----------------------------------------------------------------
|
-- Fscl 100KHz 400KHz
|
-- Fscl 100KHz 400KHz
|
-- Th_scl 4.0us 0.6us High period of SCL
|
-- Th_scl 4.0us 0.6us High period of SCL
|
-- Tl_scl 4.7us 1.3us Low 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:sta 4.7us 0.6us setup time for a repeated start condition
|
-- Tsu:sto 4.0us 0.6us setup time for a stop conditon
|
-- 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
|
-- Tbuf 4.7us 1.3us Bus free time between a stop and start condition
|
--
|
--
|
|
|
library ieee;
|
library ieee;
|
use ieee.std_logic_1164.all;
|
use ieee.std_logic_1164.all;
|
use ieee.std_logic_arith.all;
|
use ieee.std_logic_arith.all;
|
|
|
entity i2c_master_bit_ctrl is
|
entity i2c_master_bit_ctrl is
|
port (
|
port (
|
clk : in std_logic;
|
clk : in std_logic;
|
rst : in std_logic;
|
rst : in std_logic;
|
nReset : in std_logic;
|
nReset : in std_logic;
|
ena : in std_logic; -- core enable signal
|
ena : in std_logic; -- core enable signal
|
|
|
clk_cnt : in unsigned(15 downto 0); -- clock prescale value
|
clk_cnt : in unsigned(15 downto 0); -- clock prescale value
|
|
|
cmd : in std_logic_vector(3 downto 0);
|
cmd : in std_logic_vector(3 downto 0);
|
cmd_ack : out std_logic;
|
cmd_ack : out std_logic; -- command completed
|
busy : out std_logic;
|
busy : out std_logic; -- i2c bus busy
|
|
al : out std_logic; -- arbitration lost
|
|
|
din : in std_logic;
|
din : in std_logic;
|
dout : out std_logic;
|
dout : out std_logic;
|
|
|
-- i2c lines
|
-- i2c lines
|
scl_i : in std_logic; -- i2c clock line input
|
scl_i : in std_logic; -- i2c clock line input
|
scl_o : out std_logic; -- i2c clock line output
|
scl_o : out std_logic; -- i2c clock line output
|
scl_oen : out std_logic; -- i2c clock line output enable, active low
|
scl_oen : out std_logic; -- i2c clock line output enable, active low
|
sda_i : in std_logic; -- i2c data line input
|
sda_i : in std_logic; -- i2c data line input
|
sda_o : out std_logic; -- i2c data line output
|
sda_o : out std_logic; -- i2c data line output
|
sda_oen : out std_logic -- i2c data line output enable, active low
|
sda_oen : out std_logic -- i2c data line output enable, active low
|
);
|
);
|
end entity i2c_master_bit_ctrl;
|
end entity i2c_master_bit_ctrl;
|
|
|
architecture structural of i2c_master_bit_ctrl is
|
architecture structural of i2c_master_bit_ctrl is
|
constant I2C_CMD_NOP : std_logic_vector(3 downto 0) := "0000";
|
constant I2C_CMD_NOP : std_logic_vector(3 downto 0) := "0000";
|
constant I2C_CMD_START : std_logic_vector(3 downto 0) := "0001";
|
constant I2C_CMD_START : std_logic_vector(3 downto 0) := "0001";
|
constant I2C_CMD_STOP : std_logic_vector(3 downto 0) := "0010";
|
constant I2C_CMD_STOP : std_logic_vector(3 downto 0) := "0010";
|
constant I2C_CMD_READ : std_logic_vector(3 downto 0) := "0100";
|
constant I2C_CMD_READ : std_logic_vector(3 downto 0) := "0100";
|
constant I2C_CMD_WRITE : std_logic_vector(3 downto 0) := "1000";
|
constant I2C_CMD_WRITE : std_logic_vector(3 downto 0) := "1000";
|
|
|
type states is (idle, start_a, start_b, start_c, start_d, start_e,
|
type states is (idle, start_a, start_b, start_c, start_d, start_e,
|
stop_a, stop_b, stop_c, stop_d, rd_a, rd_b, rd_c, rd_d, wr_a, wr_b, wr_c, wr_d);
|
stop_a, stop_b, stop_c, stop_d, rd_a, rd_b, rd_c, rd_d, wr_a, wr_b, wr_c, wr_d);
|
signal c_state : states;
|
signal c_state : states;
|
|
|
signal iscl_oen, isda_oen : std_logic; -- internal I2C lines
|
signal iscl_oen, isda_oen : std_logic; -- internal I2C lines
|
signal sSCL, sSDA : std_logic; -- synchronized SCL and SDA inputs
|
signal sda_chk : std_logic; -- check SDA status (multi-master arbitration)
|
signal dscl_oen : std_logic; -- delayed scl_oen signals
|
signal dscl_oen : std_logic; -- delayed scl_oen signals
|
|
signal sSCL, sSDA : std_logic; -- synchronized SCL and SDA inputs
|
signal clk_en, slave_wait :std_logic; -- clock generation signals
|
signal clk_en, slave_wait :std_logic; -- clock generation signals
|
-- signal cnt : unsigned(15 downto 0) := clk_cnt; -- clock divider counter (simulation)
|
-- signal cnt : unsigned(15 downto 0) := clk_cnt; -- clock divider counter (simulation)
|
signal cnt : unsigned(15 downto 0); -- clock divider counter (synthesis)
|
signal cnt : unsigned(15 downto 0); -- clock divider counter (synthesis)
|
|
|
begin
|
begin
|
-- synchronize SCL and SDA inputs
|
-- whenever the slave is not ready it can delay the cycle by pulling SCL low
|
synch_scl_sda: process(clk)
|
|
begin
|
|
if (clk'event and clk = '1') then
|
|
sSCL <= scl_i;
|
|
sSDA <= sda_i;
|
|
end if;
|
|
end process synch_SCL_SDA;
|
|
|
|
-- delay scl_oen
|
-- delay scl_oen
|
process (clk)
|
process (clk)
|
begin
|
begin
|
if (clk'event and clk = '1') then
|
if (clk'event and clk = '1') then
|
dscl_oen <= iscl_oen;
|
dscl_oen <= iscl_oen;
|
end if;
|
end if;
|
end process;
|
end process;
|
|
|
-- whenever the slave is not ready it can delay the cycle by pulling SCL low
|
|
slave_wait <= dscl_oen and not sSCL;
|
slave_wait <= dscl_oen and not sSCL;
|
|
|
-- generate clk enable signal
|
-- generate clk enable signal
|
gen_clken: process(clk, nReset)
|
gen_clken: process(clk, nReset)
|
begin
|
begin
|
if (nReset = '0') then
|
if (nReset = '0') then
|
cnt <= (others => '0');
|
cnt <= (others => '0');
|
clk_en <= '1';
|
clk_en <= '1';
|
elsif (clk'event and clk = '1') then
|
elsif (clk'event and clk = '1') then
|
if (rst = '1') then
|
if (rst = '1') then
|
cnt <= (others => '0');
|
cnt <= (others => '0');
|
clk_en <= '1';
|
clk_en <= '1';
|
else
|
else
|
if ( (cnt = 0) or (ena = '0') ) then
|
if ( (cnt = 0) or (ena = '0') ) then
|
clk_en <= '1';
|
if (slave_wait = '0') then
|
cnt <= clk_cnt;
|
cnt <= clk_cnt;
|
|
clk_en <= '1';
|
|
else
|
|
cnt <= cnt;
|
|
clk_en <= '0';
|
|
end if;
|
else
|
else
|
if (slave_wait = '0') then
|
if (slave_wait = '0') then
|
cnt <= cnt -1;
|
cnt <= cnt -1;
|
end if;
|
end if;
|
clk_en <= '0';
|
clk_en <= '0';
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end process gen_clken;
|
end process gen_clken;
|
|
|
|
|
-- generate bus status controller
|
-- generate bus status controller
|
bus_status_ctrl: block
|
bus_status_ctrl: block
|
signal dSDA : std_logic;
|
signal dSCL, dSDA : std_logic; -- delayes sSCL and sSDA
|
signal sta_condition : std_logic;
|
signal sta_condition : std_logic; -- start detected
|
signal sto_condition : std_logic;
|
signal sto_condition : std_logic; -- stop detected
|
|
signal cmd_stop, dcmd_stop : std_logic; -- STOP command
|
signal ibusy : std_logic;
|
signal ibusy : std_logic; -- internal busy signal
|
|
begin
|
|
-- synchronize SCL and SDA inputs
|
|
synch_scl_sda: process(clk)
|
begin
|
begin
|
|
if (clk'event and clk = '1') then
|
|
sSCL <= scl_i;
|
|
sSDA <= sda_i;
|
|
|
|
dSCL <= sSCL;
|
|
dSDA <= sSDA;
|
|
end if;
|
|
end process synch_SCL_SDA;
|
|
|
-- detect start condition => detect falling edge on SDA while SCL is high
|
-- detect start condition => detect falling edge on SDA while SCL is high
|
-- detect stop condition => detect rising edge on SDA while SCL is high
|
-- detect stop condition => detect rising edge on SDA while SCL is high
|
detect_sta_sto: process(clk)
|
detect_sta_sto: process(clk)
|
begin
|
begin
|
if (clk'event and clk = '1') then
|
if (clk'event and clk = '1') then
|
dSDA <= sSDA; -- generate a delayed version of sSDA
|
|
|
|
sta_condition <= (not sSDA and dSDA) and sSCL;
|
sta_condition <= (not sSDA and dSDA) and sSCL;
|
sto_condition <= (sSDA and not dSDA) and sSCL;
|
sto_condition <= (sSDA and not dSDA) and sSCL;
|
end if;
|
end if;
|
end process detect_sta_sto;
|
end process detect_sta_sto;
|
|
|
-- generate bus busy signal
|
-- generate i2c-bus busy signal
|
gen_busy: process(clk, nReset)
|
gen_busy: process(clk, nReset)
|
begin
|
begin
|
if (nReset = '0') then
|
if (nReset = '0') then
|
ibusy <= '0';
|
ibusy <= '0';
|
elsif (clk'event and clk = '1') then
|
elsif (clk'event and clk = '1') then
|
if (rst = '1') then
|
if (rst = '1') then
|
ibusy <= '0';
|
ibusy <= '0';
|
else
|
else
|
ibusy <= (sta_condition or ibusy) and not sto_condition;
|
ibusy <= (sta_condition or ibusy) and not sto_condition;
|
end if;
|
end if;
|
end if;
|
end if;
|
end process gen_busy;
|
end process gen_busy;
|
|
|
-- assign output
|
|
busy <= ibusy;
|
busy <= ibusy;
|
|
|
|
|
|
-- generate arbitration lost signal
|
|
gen_al: process(clk)
|
|
begin
|
|
if (clk'event and clk = '1') then
|
|
if (cmd = I2C_CMD_STOP) then
|
|
cmd_stop <= '1';
|
|
else
|
|
cmd_stop <= '0';
|
|
end if;
|
|
dcmd_stop <= cmd_stop;
|
|
|
|
al <= (sda_chk and not sSDA and isda_oen) or (sto_condition and not dcmd_stop);
|
|
end if;
|
|
end process gen_al;
|
|
|
|
-- generate dout signal, store dout on rising edge of SCL
|
|
gen_dout: process(clk)
|
|
begin
|
|
if (clk'event and clk = '1') then
|
|
if (sSCL = '1' and dSCL = '0') then
|
|
dout <= sSDA;
|
|
end if;
|
|
end if;
|
|
end process gen_dout;
|
end block bus_status_ctrl;
|
end block bus_status_ctrl;
|
|
|
|
|
-- generate statemachine
|
-- generate statemachine
|
nxt_state_decoder : process (clk, nReset, c_state, cmd)
|
nxt_state_decoder : process (clk, nReset, c_state, cmd)
|
begin
|
begin
|
if (nReset = '0') then
|
if (nReset = '0') then
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '0';
|
cmd_ack <= '0';
|
dout <= '0';
|
|
iscl_oen <= '1';
|
iscl_oen <= '1';
|
isda_oen <= '1';
|
isda_oen <= '1';
|
|
sda_chk <= '0';
|
elsif (clk'event and clk = '1') then
|
elsif (clk'event and clk = '1') then
|
if (rst = '1') then
|
if (rst = '1') then
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '0';
|
cmd_ack <= '0';
|
dout <= '0';
|
|
iscl_oen <= '1';
|
iscl_oen <= '1';
|
isda_oen <= '1';
|
isda_oen <= '1';
|
|
sda_chk <= '0';
|
else
|
else
|
cmd_ack <= '0'; -- default no acknowledge
|
cmd_ack <= '0'; -- default no acknowledge
|
|
|
if (clk_en = '1') then
|
if (clk_en = '1') then
|
case (c_state) is
|
case (c_state) is
|
-- idle
|
-- idle
|
when idle =>
|
when idle =>
|
case cmd is
|
case cmd is
|
when I2C_CMD_START => c_state <= start_a;
|
when I2C_CMD_START => c_state <= start_a;
|
when I2C_CMD_STOP => c_state <= stop_a;
|
when I2C_CMD_STOP => c_state <= stop_a;
|
when I2C_CMD_WRITE => c_state <= wr_a;
|
when I2C_CMD_WRITE => c_state <= wr_a;
|
when I2C_CMD_READ => c_state <= rd_a;
|
when I2C_CMD_READ => c_state <= rd_a;
|
when others => c_state <= idle; -- NOP command
|
when others => c_state <= idle; -- NOP command
|
end case;
|
end case;
|
|
|
iscl_oen <= iscl_oen; -- keep SCL in same state
|
iscl_oen <= iscl_oen; -- keep SCL in same state
|
isda_oen <= isda_oen; -- keep SDA in same state
|
isda_oen <= isda_oen; -- keep SDA in same state
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
-- start
|
-- start
|
when start_a =>
|
when start_a =>
|
c_state <= start_b;
|
c_state <= start_b;
|
iscl_oen <= iscl_oen; -- keep SCL in same state (for repeated start)
|
iscl_oen <= iscl_oen; -- keep SCL in same state (for repeated start)
|
isda_oen <= '1'; -- set SDA high
|
isda_oen <= '1'; -- set SDA high
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when start_b =>
|
when start_b =>
|
c_state <= start_c;
|
c_state <= start_c;
|
iscl_oen <= '1'; -- set SCL high
|
iscl_oen <= '1'; -- set SCL high
|
isda_oen <= '1'; -- keep SDA high
|
isda_oen <= '1'; -- keep SDA high
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when start_c =>
|
when start_c =>
|
c_state <= start_d;
|
c_state <= start_d;
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= '0'; -- set SDA low
|
isda_oen <= '0'; -- set SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when start_d =>
|
when start_d =>
|
c_state <= start_e;
|
c_state <= start_e;
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= '0'; -- keep SDA low
|
isda_oen <= '0'; -- keep SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when start_e =>
|
when start_e =>
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '1'; -- command completed
|
cmd_ack <= '1'; -- command completed
|
iscl_oen <= '0'; -- set SCL low
|
iscl_oen <= '0'; -- set SCL low
|
isda_oen <= '0'; -- keep SDA low
|
isda_oen <= '0'; -- keep SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
-- stop
|
-- stop
|
when stop_a =>
|
when stop_a =>
|
c_state <= stop_b;
|
c_state <= stop_b;
|
iscl_oen <= '0'; -- keep SCL disabled
|
iscl_oen <= '0'; -- keep SCL low
|
isda_oen <= '0'; -- set SDA low
|
isda_oen <= '0'; -- set SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when stop_b =>
|
when stop_b =>
|
c_state <= stop_c;
|
c_state <= stop_c;
|
iscl_oen <= '1'; -- set SCL high
|
iscl_oen <= '1'; -- set SCL high
|
isda_oen <= '0'; -- keep SDA low
|
isda_oen <= '0'; -- keep SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when stop_c =>
|
when stop_c =>
|
c_state <= stop_d;
|
c_state <= stop_d;
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= '0'; -- keep SDA low
|
isda_oen <= '0'; -- keep SDA low
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when stop_d =>
|
when stop_d =>
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '1'; -- command completed
|
cmd_ack <= '1'; -- command completed
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= '1'; -- set SDA high
|
isda_oen <= '1'; -- set SDA high
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
-- read
|
-- read
|
when rd_a =>
|
when rd_a =>
|
c_state <= rd_b;
|
c_state <= rd_b;
|
iscl_oen <= '0'; -- keep SCL low
|
iscl_oen <= '0'; -- keep SCL low
|
isda_oen <= '1'; -- tri-state SDA
|
isda_oen <= '1'; -- tri-state SDA
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when rd_b =>
|
when rd_b =>
|
c_state <= rd_c;
|
c_state <= rd_c;
|
iscl_oen <= '1'; -- set SCL high
|
iscl_oen <= '1'; -- set SCL high
|
isda_oen <= '1'; -- tri-state SDA
|
isda_oen <= '1'; -- tri-state SDA
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when rd_c =>
|
when rd_c =>
|
c_state <= rd_d;
|
c_state <= rd_d;
|
dout <= sSDA;
|
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= '1'; -- tri-state SDA
|
isda_oen <= '1'; -- tri-state SDA
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
when rd_d =>
|
when rd_d =>
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '1'; -- command completed
|
cmd_ack <= '1'; -- command completed
|
iscl_oen <= '0'; -- set SCL low
|
iscl_oen <= '0'; -- set SCL low
|
isda_oen <= '1'; -- tri-state SDA
|
isda_oen <= '1'; -- tri-state SDA
|
|
sda_chk <= '0'; -- don't check SDA
|
|
|
-- write
|
-- write
|
when wr_a =>
|
when wr_a =>
|
c_state <= wr_b;
|
c_state <= wr_b;
|
iscl_oen <= '0'; -- keep SCL low
|
iscl_oen <= '0'; -- keep SCL low
|
isda_oen <= din; -- set SDA
|
isda_oen <= din; -- set SDA
|
|
sda_chk <= '0'; -- don't check SDA (SCL low)
|
|
|
when wr_b =>
|
when wr_b =>
|
c_state <= wr_c;
|
c_state <= wr_c;
|
iscl_oen <= '1'; -- set SCL high
|
iscl_oen <= '1'; -- set SCL high
|
isda_oen <= din; -- keep SDA
|
isda_oen <= din; -- keep SDA
|
|
sda_chk <= '1'; -- check SDA
|
|
|
when wr_c =>
|
when wr_c =>
|
c_state <= wr_d;
|
c_state <= wr_d;
|
iscl_oen <= '1'; -- keep SCL high
|
iscl_oen <= '1'; -- keep SCL high
|
isda_oen <= din; -- keep SDA
|
isda_oen <= din; -- keep SDA
|
|
sda_chk <= '1'; -- check SDA
|
|
|
when wr_d =>
|
when wr_d =>
|
c_state <= idle;
|
c_state <= idle;
|
cmd_ack <= '1'; -- command completed
|
cmd_ack <= '1'; -- command completed
|
iscl_oen <= '0'; -- set SCL low
|
iscl_oen <= '0'; -- set SCL low
|
isda_oen <= din; -- keep SDA
|
isda_oen <= din; -- keep SDA
|
|
sda_chk <= '0'; -- don't check SDA (SCL low)
|
|
|
when others =>
|
when others =>
|
|
|
end case;
|
end case;
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end process nxt_state_decoder;
|
end process nxt_state_decoder;
|
|
|
|
|
-- assign outputs
|
-- assign outputs
|
scl_o <= '0';
|
scl_o <= '0';
|
scl_oen <= iscl_oen;
|
scl_oen <= iscl_oen;
|
sda_o <= '0';
|
sda_o <= '0';
|
sda_oen <= isda_oen;
|
sda_oen <= isda_oen;
|
end architecture structural;
|
end architecture structural;
|
|
|
