I2C controller core之Bit controller(05)
6 generate statemachine
1 -- port
cmd_ack : out std_logic; -- command completed 4 -- architecture
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);
signal c_state : states;
signal iscl_oen, isda_oen : std_logic; -- internal I2C lines
signal sda_chk : std_logic; -- check SDA status (multi-master arbitration) 11 -- statemachine
nxt_state_decoder : process (clk, nRst)
begin
if (nRst = '') then
c_state <= idle;
cmd_ack <= '';
iscl_oen <= '';
isda_oen <= '';
sda_chk <= '';
elsif (clk'event and clk = '') then
if (rst = '' or ial = '') then
c_state <= idle;
cmd_ack <= '';
iscl_oen <= '';
isda_oen <= '';
sda_chk <= '';
else
cmd_ack <= ''; -- default no acknowledge if (clk_en = '') then
case (c_state) is
-- idle
when idle =>
case cmd is
when I2C_CMD_START => c_state <= start_a;
when I2C_CMD_STOP => c_state <= stop_a;
when I2C_CMD_WRITE => c_state <= wr_a;
when I2C_CMD_READ => c_state <= rd_a;
when others => c_state <= idle; -- NOP command
end case; iscl_oen <= iscl_oen; -- keep SCL in same state
isda_oen <= isda_oen; -- keep SDA in same state
sda_chk <= ''; -- don't check SDA -- start
when start_a =>
c_state <= start_b;
iscl_oen <= iscl_oen; -- keep SCL in same state (for repeated start)
isda_oen <= ''; -- set SDA high
sda_chk <= ''; -- don't check SDA when start_b =>
c_state <= start_c;
iscl_oen <= ''; -- set SCL high
isda_oen <= ''; -- keep SDA high
sda_chk <= ''; -- don't check SDA when start_c =>
c_state <= start_d;
iscl_oen <= ''; -- keep SCL high
isda_oen <= ''; -- set SDA low
sda_chk <= ''; -- don't check SDA when start_d =>
c_state <= start_e;
iscl_oen <= ''; -- keep SCL high
isda_oen <= ''; -- keep SDA low
sda_chk <= ''; -- don't check SDA when start_e =>
c_state <= idle;
cmd_ack <= ''; -- command completed
iscl_oen <= ''; -- set SCL low
isda_oen <= ''; -- keep SDA low
sda_chk <= ''; -- don't check SDA -- stop
when stop_a =>
c_state <= stop_b;
iscl_oen <= ''; -- keep SCL low
isda_oen <= ''; -- set SDA low
sda_chk <= ''; -- don't check SDA when stop_b =>
c_state <= stop_c;
iscl_oen <= ''; -- set SCL high
isda_oen <= ''; -- keep SDA low
sda_chk <= ''; -- don't check SDA when stop_c =>
c_state <= stop_d;
iscl_oen <= ''; -- keep SCL high
isda_oen <= ''; -- keep SDA low
sda_chk <= ''; -- don't check SDA when stop_d =>
c_state <= idle;
cmd_ack <= ''; -- command completed
iscl_oen <= ''; -- keep SCL high
isda_oen <= ''; -- set SDA high
sda_chk <= ''; -- don't check SDA -- read
when rd_a =>
c_state <= rd_b;
iscl_oen <= ''; -- keep SCL low
isda_oen <= ''; -- tri-state SDA
sda_chk <= ''; -- don't check SDA when rd_b =>
c_state <= rd_c;
iscl_oen <= ''; -- set SCL high
isda_oen <= ''; -- tri-state SDA
sda_chk <= ''; -- don't check SDA when rd_c =>
c_state <= rd_d;
iscl_oen <= ''; -- keep SCL high
isda_oen <= ''; -- tri-state SDA
sda_chk <= ''; -- don't check SDA when rd_d =>
c_state <= idle;
cmd_ack <= ''; -- command completed
iscl_oen <= ''; -- set SCL low
isda_oen <= ''; -- tri-state SDA
sda_chk <= ''; -- don't check SDA -- write
when wr_a =>
c_state <= wr_b;
iscl_oen <= ''; -- keep SCL low
isda_oen <= din; -- set SDA
sda_chk <= ''; -- don't check SDA (SCL low) when wr_b =>
c_state <= wr_c;
iscl_oen <= ''; -- set SCL high
isda_oen <= din; -- keep SDA
sda_chk <= ''; -- don't check SDA yet
-- Allow some more time for SDA and SCL to settle when wr_c =>
c_state <= wr_d;
iscl_oen <= ''; -- keep SCL high
isda_oen <= din; -- keep SDA
sda_chk <= ''; -- check SDA when wr_d =>
c_state <= idle;
cmd_ack <= ''; -- command completed
iscl_oen <= ''; -- set SCL low
isda_oen <= din; -- keep SDA
sda_chk <= ''; -- don't check SDA (SCL low) when others => end case;
end if;
end if;
end if;
end process nxt_state_decoder;
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