/* ************************************************************ */
declare RAM_FIFO {
    input       DB_i[8] ;       // Write Data (in)
    output      DB_o[8] ;       // Read Data (out)

    input       WEN_i ;         // Write enable (in)
    input       REN_i ;         // Read enable (in)

    output      FULL ;          // FIFO full flag.
    output      EMPTY ;         // FIFO empty flag.
}

/* ************************************************************ */
// Declare module
module RAM_FIFO {

/* ************************************************************ */
// Internal operation signals
    mem     mem_array [16][8] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } ;
                                // Declare memory array with INIT.
    reg     reg_DB_o[8] ;

    reg     wr_ptr[4] = 0 ;     // Write pointer ( current )
    reg     rd_ptr[4] = 0 ;     // Read  pointer ( current )
    wire    next_wr_ptr[4] ;
    wire    next_rd_ptr[4] ;

    wire    internal_FULL ;
    wire    internal_EMPTY ;

    func_self   Check_FULL_flag() ;
    func_self   Check_EMPTY_flag() ;

/* ************************************************************ */
// Equation
{
// ************************ //
// FIFO write side.
    if ( WEN_i & ~internal_FULL ) {
        mem_array[wr_ptr] := DB_i ; // Store a current write data to memory array.
        wr_ptr := next_wr_ptr ;     // Update NEW write pointer
    }

    next_wr_ptr = wr_ptr + 4'b1 ;

    Check_FULL_flag() ;

// ************************ //
// FIFO read side.
    if ( REN_i & ~internal_EMPTY ) {
        reg_DB_o := mem_array[rd_ptr] ;
                            // Read-out memory array to internal output regs.
        rd_ptr := next_rd_ptr ;     // Update NEW write pointer
    }

    DB_o = reg_DB_o ;

    next_rd_ptr = rd_ptr + 4'b1 ;

    Check_EMPTY_flag() ;    

    FULL    = internal_FULL ;
    EMPTY   = internal_EMPTY ;

}

func Check_FULL_flag {
    any {
        next_wr_ptr == rd_ptr   : internal_FULL = 1'b1 ;    // Set FULL flag.
        else                    : internal_FULL = 1'b0 ;
    }
}

func Check_EMPTY_flag {
    any {
        rd_ptr == wr_ptr        : internal_EMPTY = 1'b1 ;   // Set FULL flag.
        else                    : internal_EMPTY = 1'b0 ;
    }
}

/* ************************************************************ */
}