I think I'm misunderstanding how Sys.Init() works. In the NestedCallVME.text example, 256 - 261 are set explicitly by the script rather than the 'caller' of Sys.Init(). So the values are 1234, -1, 2, -3, -4 rather than what I would expect, which would be 261 261, 256, -3, -4. Which are the values of the first 5 'registers' upon the calling of Sys.Init(). Is this correct? It doesn't appear that the calling of Sys.Init() within the VMemulator actually does anything. Basically, it doesn't seem like Sys.Init() actually saves its stack frame. It just increments SP automatically.