I understand that SETB in 8051 sets a bit in a particular register. So if it is addressed as:
SETB P1.5 or SETB ACC.2, it sets the 5th bit of port1 or 2nd bit of ACC.
But what does SETB 53h mean? Which bit of which register does it set? There are other similar instructions like CPL 64h or JB 53h.