-- Burst Read Single Write
            IF Write_burst_mode = '1' AND Data_in_enable = '1' THEN
                Data_in_enable := '0';
            END IF;

            -- Data counter
            IF Burst_length_1 = '1' THEN
                IF Burst_counter >= 1 THEN
                    IF Data_in_enable = '1' THEN
                        Data_in_enable := '0';
                    ELSIF Data_out_enable = '1' THEN
                        Data_out_enable := '0';
                    END IF;
                END IF;
            ELSIF Burst_length_2 = '1' THEN
                IF Burst_counter >= 2 THEN
                    IF Data_in_enable = '1' THEN
                        Data_in_enable := '0';
                    ELSIF Data_out_enable = '1' THEN
                        Data_out_enable := '0';
                    END IF;
                END IF;
            ELSIF Burst_length_4 = '1' THEN
                IF Burst_counter >= 4 THEN
                    IF Data_in_enable = '1' THEN
                        Data_in_enable := '0';
                    ELSIF Data_out_enable = '1' THEN
                        Data_out_enable := '0';
                    END IF;
                END IF;
            ELSIF Burst_length_8 = '1' THEN
                IF Burst_counter >= 8 THEN
                    IF Data_in_enable = '1' THEN
                        Data_in_enable := '0';
                    ELSIF Data_out_enable = '1' THEN
                        Data_out_enable := '0';
                    END IF;
                END IF;
            END IF;
        END;

    BEGIN
        WAIT ON Sys_clk, RAS_clk;
        IF Sys_clk'event AND Sys_clk = '1' THEN
            -- Internal Command Pipeline
            Command(0) := Command(1);
            Command(1) := Command(2);
            Command(2) := Command(3);
            Command(3) := NOP;

            Col_addr(0) := Col_addr(1);
            Col_addr(1) := Col_addr(2);
            Col_addr(2) := Col_addr(3);
            Col_addr(3) := (OTHERS => '0');

            Bank_addr(0) := Bank_addr(1);
            Bank_addr(1) := Bank_addr(2);
            Bank_addr(2) := Bank_addr(3);
            Bank_addr(3) := "00";

            Bank_precharge(0) := Bank_precharge(1);
            Bank_precharge(1) := Bank_precharge(2);
            Bank_precharge(2) := Bank_precharge(3);
            Bank_precharge(3) := "00";

            A10_precharge(0) := A10_precharge(1);
            A10_precharge(1) := A10_precharge(2);
            A10_precharge(2) := A10_precharge(3);
            A10_precharge(3) := '0';

            -- Operation Decode (Optional for showing current command on posedge clock / debug feature)
            IF Active_enable = '1' THEN
                Operation <= ACT;
            ELSIF Aref_enable = '1' THEN
                Operation <= A_REF;
            ELSIF Burst_term = '1' THEN
                Operation <= BST;
            ELSIF Mode_reg_enable = '1' THEN
                Operation <= LMR;
            ELSIF Prech_enable = '1' THEN
                Operation <= PRECH;
            ELSIF Read_enable = '1' THEN
                IF Addr(10) = '0' THEN
                    Operation <= READ;
                ELSE
                    Operation <= READ_A;
                END IF;
            ELSIF Write_enable = '1' THEN
                IF Addr(10) = '0' THEN
                    Operation <= WRITE;
                ELSE
                    Operation <= WRITE_A;
                END IF;
            ELSE
                Operation <= NOP;
            END IF;

            -- Dqm pipeline for Read
            Dqm_reg0 := Dqm_reg1;
	        Dqm_reg1 := Dqm;
			-- Read or Write with Auto Precharge Counter
            IF Auto_precharge (0) = '1' THEN
                Count_precharge (0) := Count_precharge (0) + 1;
            END IF;
            IF Auto_precharge (1) = '1' THEN
                Count_precharge (1) := Count_precharge (1) + 1;
            END IF;
            IF Auto_precharge (2) = '1' THEN
                Count_precharge (2) := Count_precharge (2) + 1;
            END IF;
            IF Auto_precharge (3) = '1' THEN
                Count_precharge (3) := Count_precharge (3) + 1;
            END IF;

            -- Auto Precharge Timer for tWR
            if (Burst_length_1 = '1' OR Write_burst_mode = '1') then
                if (Count_precharge(0) = 1) then
                    Count_time(0) := NOW;
                end if;
                if (Count_precharge(1) = 1) then
                    Count_time(1) := NOW;
                end if;
                if (Count_precharge(2) = 1) then
                    Count_time(2) := NOW;
                end if;
                if (Count_precharge(3) = 1) then
                    Count_time(3) := NOW;
                end if;
            elsif (Burst_length_2 = '1') then
                if (Count_precharge(0) = 2) then
                    Count_time(0) := NOW;
                end if;
                if (Count_precharge(1) = 2) then
                    Count_time(1) := NOW;
                end if;
                if (Count_precharge(2) = 2) then
                    Count_time(2) := NOW;
                end if;
                if (Count_precharge(3) = 2) then
                    Count_time(3) := NOW;
                end if;
            elsif (Burst_length_4 = '1') then
                if (Count_precharge(0) = 4) then
                    Count_time(0) := NOW;
                end if;
                if (Count_precharge(1) = 4) then
                    Count_time(1) := NOW;
                end if;
                if (Count_precharge(2) = 4) then
                    Count_time(2) := NOW;
                end if;
                if (Count_precharge(3) = 4) then
                    Count_time(3) := NOW;
                end if;
            elsif (Burst_length_8 = '1') then
                if (Count_precharge(0) = 8) then
                    Count_time(0) := NOW;
                end if;
                if (Count_precharge(1) = 8) then
                    Count_time(1) := NOW;
                end if;
                if (Count_precharge(2) = 8) then
                    Count_time(2) := NOW;
                end if;
                if (Count_precharge(3) = 8) then
                    Count_time(3) := NOW;
                end if;
            end if;

            -- tMRD Counter
            MRD_chk := MRD_chk + 1;

            -- tWR Counter
            WR_counter(0) := WR_counter(0) + 1;
            WR_counter(1) := WR_counter(1) + 1;
            WR_counter(2) := WR_counter(2) + 1;
            WR_counter(3) := WR_counter(3) + 1;

            -- Auto Refresh
            IF Aref_enable = '1' THEN
                -- Auto Refresh to Auto Refresh
                ASSERT (NOW - RC_chk >= tRC)
                    REPORT "tRC violation during Auto Refresh"
                    SEVERITY WARNING;
                -- Precharge to Auto Refresh
                ASSERT (NOW - RP_chk0 >= tRP OR NOW - RP_chk1 >= tRP OR NOW - RP_chk2 >= tRP OR NOW - RP_chk3 >= tRP)
                    REPORT "tRP violation during Auto Refresh"
                    SEVERITY WARNING;
                -- All banks must be idle before refresh
                IF (Pc_b3 = '0' OR Pc_b2 = '0' OR Pc_b1 = '0' OR Pc_b0 = '0') THEN
                    ASSERT (FALSE)
                        REPORT "All banks must be Precharge before Auto Refresh"
                        SEVERITY WARNING;
                END IF;
                -- Record current tRC time
                RC_chk := NOW;
            END IF;

            -- Load Mode Register
            IF Mode_reg_enable = '1' THEN
                Mode_reg <= Addr;
                IF (Pc_b3 = '0' OR Pc_b2 = '0' OR Pc_b1 = '0' OR Pc_b0 = '0') THEN
                    ASSERT (FALSE)
                        REPORT "All bank must be Precharge before Load Mode Register"
                        SEVERITY WARNING;
                END IF;
                -- REF to LMR
                ASSERT (NOW - RC_chk >= tRC)
                    REPORT "tRC violation during Load Mode Register"
                    SEVERITY WARNING;
                -- LMR to LMR
                ASSERT (MRD_chk >= tMRD)
                    REPORT "tMRD violation during Load Mode Register"
                    SEVERITY WARNING;
                -- Record current tMRD time
                MRD_chk := 0;
            END IF;

            -- Active Block (latch Bank and Row Address)
            IF Active_enable = '1' THEN
                IF Ba = "00" AND Pc_b0 = '1' THEN
                    Act_b0 := '1';
                    Pc_b0 := '0';
                    B0_row_addr := Addr;
                    RCD_chk0 := NOW;
                    RAS_chk0 := NOW;
                    -- Precharge to Active Bank 0
                    ASSERT (NOW - RP_chk0 >= tRP)
                        REPORT "tRP violation during Activate Bank 0"
                        SEVERITY WARNING;
                ELSIF Ba = "01" AND Pc_b1 = '1' THEN
                    Act_b1 := '1';
                    Pc_b1 := '0';
                    B1_row_addr := Addr;
                    RCD_chk1 := NOW;
                    RAS_chk1 := NOW;
                    -- Precharge to Active Bank 1
                    ASSERT (NOW - RP_chk1 >= tRP)
                        REPORT "tRP violation during Activate Bank 1"
                        SEVERITY WARNING;
                ELSIF Ba = "10" AND Pc_b2 = '1' THEN
                    Act_b2 := '1';
                    Pc_b2 := '0';
                    B2_row_addr := Addr;
                    RCD_chk2 := NOW;
                    RAS_chk2 := NOW;
                    -- Precharge to Active Bank 2
                    ASSERT (NOW - RP_chk2 >= tRP)
                        REPORT "tRP violation during Activate Bank 2"
                        SEVERITY WARNING;
                ELSIF Ba = "11" AND Pc_b3 = '1' THEN
                    Act_b3 := '1';
                    Pc_b3 := '0';
                    B3_row_addr := Addr;
                    RCD_chk3 := NOW;
                    RAS_chk3 := NOW;
                    -- Precharge to Active Bank 3
                    ASSERT (NOW - RP_chk3 >= tRP)
                        REPORT "tRP violation during Activate Bank 3"
                        SEVERITY WARNING;
                ELSIF Ba = "00" AND Pc_b0 = '0' THEN
                    ASSERT (FALSE)
                        REPORT "Bank 0 is not Precharged"
                        SEVERITY WARNING;
                ELSIF Ba = "01" AND Pc_b1 = '0' THEN
                    ASSERT (FALSE)
                        REPORT "Bank 1 is not Precharged"
                        SEVERITY WARNING;
                ELSIF Ba = "10" AND Pc_b2 = '0' THEN
                    ASSERT (FALSE)
                        REPORT "Bank 2 is not Precharged"
                        SEVERITY WARNING;
                ELSIF Ba = "11" AND Pc_b3 = '0' THEN
                    ASSERT (FALSE)
                        REPORT "Bank 3 is not Precharged"
                        SEVERITY WARNING;
                END IF;
                -- Active Bank A to Active Bank B
                IF ((Previous_bank /= Ba) AND (NOW - RRD_chk < tRRD)) THEN
                    ASSERT (FALSE)
                        REPORT "tRRD violation during Activate"
                        SEVERITY WARNING;
                END IF;
                -- LMR to ACT
                ASSERT (MRD_chk >= tMRD)
                    REPORT "tMRD violation during Activate"
                    SEVERITY WARNING;
                -- AutoRefresh to Activate
                ASSERT (NOW - RC_chk >= tRC)
                    REPORT "tRC violation during Activate"
                    SEVERITY WARNING;
                -- Record variable for checking violation
                RRD_chk := NOW;