DPSEL is not the DPTR, it selects one of the two DPTR registers in some 8052 variants.

The basic register is the DPTR, it is one of the only 16 bit registers in the processor, which makes it uniquely tricky to play with since everything else is 8 bits. Mnay operations on the DPTR split the task into working on DPL, the lower 8 bits of the DPTR and DPH, the upper 8 bits.

There is an INC DPTR instruction, but no DEC instruction.

Steve