Ian, note , what is that "whatever" pushed onto the stack last: it is the content of the stack before the first push - i.e. the return address - recovered by the xch a,@r0 instructions (r0 has been filled by sp and decremented down to the position of return address).

It is similar with the other, restore context, routine - first the return address gets popped out into dptr, but later it gets stored back into stack so after all popsare done it is just at the top of the stack. Btw, this is the key to answer to Oleg's puzzle.

Jan Waclawek