Correct Answer - Option 2 : RA A
DPTR – Data pointer is the 8051’s only user-accessible 16 bit (2 - byte) register. DPTR is meant for pointing to data. It is used by the 8051 to access external memory using the address indicated by DPTR. It is used to store a 2-byte value.
Let us go by options one by one,
MOVX:
The MOVX instruction moves a byte to or from External Memory into or from the Accumulator.
MOVX A, @DPTR
It means that the data stored in the address specified or loaded in DPTR is moved or loaded into A register or Accumulator.
MOVX @DPTR, A
It means the Accumulator is moved to the 16-bit External Memory address indicated by DPTR.
MOV:
This mode specifies data by its value.
MOV DPTR# 2500
This instruction set is used to read data of external RAM at location 2500.
DA :
The DA instruction adjusts the eight-bit value of the register resulting from the earlier addition of two variables (each in packed-BCD format), producing two four-bit digits. .
