Why does the pulse command not send out when using the pulse command in the STL step instruction?

Many people are accustomed to programming with STL step instructions, because this way of programming is fast, the process is clear, and it is easy to modify; but due to the special scan mode of our PLC, we often encounter conditions when using pulse instructions in STL step instructions. The problem is that the pulse is not sent. The solution is to put our pulse instruction outside the STL step instruction.

Problem case: In the following programming mode, write DRVA absolute positioning instructions in STL and execute them cyclically. There will be a problem that it can run for the first time and no pulse can be sent the second time.

Solution examples:

NOTE：In WECON PLC, step S jumps to the next step. If there is no RET in the middle, it belongs to the same cycle. This will cause the flag bit M8029 to trigger continuously. This problem can be avoided in the above example.