architecture Behavioral of neuron is
signal MembranePotential: integer range smallest_int to maximum_int :=0;
signal Refract_period: integer range 0 to refractory_len:=0;
signal Refract_en: std_logic;
signal SPIKEOUT: std_logic :='0';
begin
process( FASTCLK)
begin
    if falling_edge(RST) then
            SPIKEOUT<='0';    
            MembranePotential<=0;
    elsif falling_edge(SLOW_CLK) then                                -- degrading membrane potential            
        if MembranePotential>MembraneThreshold then                -- spike
            MembranePotential<=0;
            SPIKEOUT<='1';
            Refract_period<=refractory_len;
        elsif MembranePotential>0 then
            MembranePotential<=MembranePotential-MembraneDegradationRate;
        elsif SPIKEOUT='1' then                                    --refractory period degradation
            Refract_period<=Refract_period -1;
            SPIKEOUT<='0';
        end if;    
    elsif falling_edge(IN_SPIKE) then                            -- adding incoming spike
        if Refract_period=0 then
            MembranePotential<=MembranePotential+conv_integer(IN_WEIGHT);
        end if;        
    end if;    
end process;
OUTPUT<=SPIKEOUT;
end Behavioral;