至少S7200在手册的附录中这样写到：
Effect of Indirect Addressing
Table F-2 shows the time required for executing the logic, or function, of the instruction when you use direct addressing of the operands and constants.
When instructions use indirectly addressed operands, the execution time for the instruction increases by 14 μs for each indirectly addressed operand used in the instruction.
使用指针间址，额外浪费14us的时间。感觉多了点。大概是因为S7200是解释执行的，间址效率不高。