The data Pointer (DPTR)

The Data Pointer (DPTR) is the 8051s only user-accessable 16-bit (2-byte) register. The Accumulator, "R" registers, and "B" register are all 1-byte values. DPTR, as the name suggests, is used to point to data. It is used by a number of commands which allow the 8051 to access external memory. When the 8051 accesses external memory it will access external memory at the address indicated by DPTR. While DPTR is most often used to point to data in external memory, many programmers often take advantge of the fact that its the only true 16-bit register available. It is often used to store 2-byte values which have nothing to do with memory locations. It consists of one 8-bit register for DPL and other 8-bit register for DPH.


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