FSUB              Subtract Real               Exception Flags: I D O U P

FSUB [[destination,] source]

       Logic:      ST(1) . ST(1) - ST, pop stack   (no operands)
                   ST . ST - memory operand        (source only)
                   ST . ST - ST(i)                 (destination, source)


     FSUB subtracts two real numbers and leaves the result on the stack.
     In the no operands form, ST(1) and ST are the implied operands. FSUB
     takes the source operand from ST and destination from ST(1).
     It does the subtraction, puts the result in ST(1), and then pops the
     stack.

  --------------------------------------------------------------------------
   Operands            Clocks         Bytes           Example
   FSUB                70-100           3             FSUB
   FSUB MEMORY_REAL    90-125+EA        5             FSUB REAL_NUMBER
   FSUB ST, ST(i)      75-105           3             FSUB ST,ST(1)
  --------------------------------------------------------------------------

        Note:          In the FSUB destination, source form, ST must
                       be one of the operands.