5182A触发器启动频率问题

我是以编程方式（使用scpi）在信号发生器中设置扫描列表，并希望触发它在外部步进，所有这些似乎都有效。
然而，5182A似乎立即从列表中的第一个频率开始...意味着当第一个（外部）触发发生时，它会移动到第二个频率。
这似乎不正确，有没有办法改变列表中的位置开始（即我需要将起始位置设置为列表中的最后一个条目），还是让第一个触发器实际启动第一个频率？
（我已经使用了较旧的8645A，它可以正确地执行此操作......这被认为是替换单元）。基本上，设置只是以下命令首先加载频率，电源和停留列表然后......：OUTP：STATe ON
：FREQuency：MODE LIST;：POWer：MODE LIST;：LIST：DWEL：TYPE LIST;：LIST：TRIGger：SOURce EXTernalRecap：频率列表F1 F2 F3 F4应该在第一次外部触发发生时开始输出F1，然后继续
F2在第二次触发时依此类推。
输出F4后，下一个触发器应该再次启动F1。非常感谢任何帮助。



     以下为原文

  I am programmatically (using scpi) setting a sweep list in the signal generator, and want to trigger it to step externally, all of which seems to work.  However, the 5182A seems to immediately start at the first frequency in the list...meaning that when the first (external) trigger occurs it moves on to the second frequency.  This does not seem correct, is there some way of either changing where in the list to start (i.e. do I need to set the start position to the last entry in the list), or make the first trigger actually initiate the first frequency? (I have used older 8645A which does this properly...this was suppose to be a replacement unit).

Basically the setup is just the following commands
The frequency, power, and dwell lists are loaded first then...
:OUTP:STATe ON
:FREQuency:MODE LIST;
:POWer:MODE LIST;
:LIST:DWEL:TYPE LIST;
:LIST:TRIGger:SOURce EXTernal

Recap:  
Frequency list F1 F2 F3 F4
It should start outputing the F1 when the first external trigger occurs, then move on to the F2 at the second trigger and so on.  After F4 is output the next trigger should start F1 again.

Any help would be greatly appreciated.