In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

PAR,

this behavior of the debugger is caused by the internal structure of the SX chips which causes that the debugger can't handle NOP instructions correctly. So, it is not possible to set a breakpoint on a NOP instruction, and single-stepping along NOP instructions also causes strange behavior. Actually, single-stepping is like continuously setting a breakpoint on the next instruction, and this is why the debugger seems to run out of sync when you try to step the NOPs. You are right, although the display is mis-leading, the SX executes all the instructions in correct order, and does not skip any of them.

Instead of the NOP, you might consider using any other single-cycle instruction but keep in mind that all other instructions modify some register contents, or the flags. For example, if you use and w, #$ff instead, this will preserve the contents of w but might change the Z flag, depending on the current contents of w. In the little loop sample code, this does not matter but it might in other contexts.

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