ControllersENGIN 341 – Advanced Digital DesignUniversity of Massachusetts Boston

Department of EngineeringDr. Filip Cuckov

Overview1. Algorithmic State Machines2. Microprogrammed Controllers

1. Algorithmic State Machines (ASM)

ASM – Parallel vs. Serial Form

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ASM Examples

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Finite State Machine (FSM) to ASM

Shift and Add Multiplier Example (Algorithm)

Shift and Add Multiplier Example (FSM)

Shift and Add Multiplier Example (Counter)

Shift and Add Multiplier Example (ASM)

Shift and Add Multiplier Example (VHDL)

State Machine Factorization using Inter-Process Communication

State Machine VHDL Formalism• VHDL implementation must

include at least 3 processes:

1. State Register (CLK)2. NS Calc. (PS, Inputs)3. Outputs Calculation

• Moore Outputs (PS)• Mealy Outputs (PS, Inputs)

• Fourth Process for Sync. Mealy4. Output Register (CLK)

Moore-Type Machine VHDL Implementationlibrary ieee;use ieee.std_logic_1164.all;use ieee.numeric_std.all;

entity MooreSM isgeneric(N : integer := 3);port(clk, rst : in std_logic;inputs : in std_logic_vector(N downto 0);outputs : out std_logic_vector(N downto 0));end entity MooreSM;

architecture Behavioral of MooreSM istype state_type is (Start, State1, State2);signal PS, NS : state_type;

begin

State_Reg : process(clk, rst) isbeginif rst = '1' then PS <= Start;elsif clk'event and clk = '1' then PS <= NS;end if;end process State_Reg;

NS_Calc : process(PS, inputs) isbegincase PS is when Start => NS <= State1; when State1 => if inputs = "0110" then NS <= State2; else NS <= State1; end if; when State2 => NS <= Start;end case;end process NS_Calc;

Moore_out : process(PS) isbegincase PS is when Start => outputs <= "0000"; when State1 => outputs <= "0110"; when State2 => outputs <= "1001";end case;end process Moore_out;

end architecture Behavioral;

Mealy-Type Machine VHDL Implementationlibrary ieee;use ieee.std_logic_1164.all;use ieee.numeric_std.all;

entity MealySM isport(clk, rst : in std_logic;A_i, B_i : in std_logic;Y_o, Z_o : out std_logic);end entity MealySM;

architecture Behavioral of MealySM issignal PS, NS : integer range 0 to 2;begin

State_Reg : process(rst, clk) isbegin if rst = '1' then PS <= 0; elsif rising_edge(clk) then PS <= NS; end if;end process State_Reg;

NS_calc : process(PS, A_i, B_i) isbegin case PS is when 0 => NS <= 1; when 1 => if (A_i and B_i) = '1' then NS <= 1; else NS <= 2; end if; when 2 => NS <= 0; end case;end process NS_calc;

Mealy_out : process(PS, A_i, B_i) isbegin Y_o <= '0'; Z_o <= '0';

case PS is when 0 => null; when 1 => if (A_i and B_i) = '1' then Y_o <= '1'; else Z_o <= '1'; end if; when 2 => null; end case;end process Mealy_out;

end architecture Behavioral;

2. Microprogrammed Controllers

Single Qualifier – Dual TransitionMeaning only one Boolean checkper state is allowed.

Still Single Qualifier – Dual Transition, butNSF assumed to be next in sequence in ROM

Microprogrammed Controllers ASM Adjust

Mealy to Moore Simplification

Microprogrammed Controllers