George,

I think that the block with stars simply reads a byte from external memory (or maybe some kind of peripheral). It modifies P2 port (inc P2) before reading, so defining the 8 most significant bits of the external address bus. And then left P2 unchanged (dec P2). The block is executed with all interrupts inhibited (clr EA, ..., setb EA).

A deeper analysis requires a further knowledge about the HW.

Regards,
Alfredo del Río.