Model a State Machine for HDL and High-Level Synthesis Code Generation - MATLAB & Simulink (original) (raw)

Main Content

The following design pattern shows MATLAB® examples of Mealy and Moore state machines which are suitable for HDL and High-Level Synthesis (HLS) code generation.

The MATLAB code in these models demonstrates best practices for writing MATLAB models for HDL and HLS code generation.

MATLAB Code for the Mealy State Machine

In a Mealy state machine, the output depends on the state and the input. In a Moore state machine, the output depends only on the state.

The following MATLAB code defines the mlhdlc_fsm_mealy function. A persistent variable represents the current state. A switch block uses the current state and input to determine the output and new state. In each case in the switch block, an if-else statement calculates the new state and output.

MATLAB Code

%#codegen function Z = mlhdlc_fsm_mealy(A) % Mealy State Machine

% y = f(x,u) : % all actions are condition actions and % outputs are function of state and input

% define states S1 = 0; S2 = 1; S3 = 2; S4 = 3;

persistent current_state; if isempty(current_state) current_state = S1;
end

% switch to new state based on the value state register switch (current_state) 

case S1,
    
    % value of output 'Z' depends both on state and inputs
    if (A)
        Z = true;
        current_state = S1;
    else
        Z = false;            
        current_state = S2;
    end
    
case S2,
    
    if (A)
        Z = false;
        current_state = S3;
    else
        Z = true;
        current_state = S2;
    end
    
case S3,
    
    if (A)
        Z = false;            
        current_state = S4;
    else
        Z = true;            
        current_state = S1;
    end
    
case S4,
    
    if (A)
        Z = true;
        current_state = S1;
    else
        Z = false;            
        current_state = S3;
    end        
    
otherwise,
    
    Z = false;

end

MATLAB Test Bench

for i = 1:100 if mod(i,2) == 0 val = mlhdlc_fsm_mealy(true); else val = mlhdlc_fsm_mealy(false); end end

MATLAB Code for the Moore State Machine

The following MATLAB code defines the mlhdlc_fsm_moore function. A persistent variable represents the current state, and a switch block uses the current state to determine the output and new state. In each case in the switch block, an if-else statement calculates the new state and output. The value of the state is represented by numerical variables.

MATLAB Code

%#codegen function Z = mlhdlc_fsm_moore(A) % Moore State Machine

% y = f(x) : % all actions are state actions and % outputs are pure functions of state only

% define states S1 = 0; S2 = 1; S3 = 2; S4 = 3;

% using persistent keyword to model state registers in hardware persistent curr_state; if isempty(curr_state) curr_state = S1;
end

% switch to new state based on the value state register switch (curr_state)

case S1,
    
    % value of output 'Z' depends only on state and not on inputs
    Z = true;
    
    % decide next state value based on inputs
    if (~A)
        curr_state = S1;
    else
        curr_state = S2;
    end
    
case S2,
    
    Z = false;
    
    if (~A)
        curr_state = S1;
    else
        curr_state = S3;
    end
    
case S3,
    
    Z = false;
    
    if (~A)
        curr_state = S2;
    else
        curr_state = S4;
    end
    
case S4,
    
    Z = true;
    if (~A)
        curr_state = S3;
    else
        curr_state = S1;
    end
    
otherwise,
    Z = false;

end

MATLAB Test Bench

for i = 1:100 if mod(i,2) == 0 val = mlhdlc_fsm_moore(true); else val = mlhdlc_fsm_moore(false); end end

See Also

codegen | coder.HdlConfig

Topics