MOVC A,@A+DPTR: Each of these addressing modes provides important flexibility. When the above instruction is executed the 8051 will check the value of R0. Since R0 holds 40h the 8051 will get the value out of Internal RAM address 40h (which holds 67h) and store it in the Accumulator. Thus, the Accumulator ends up holding 67h. MOVC instruction Example: MOV A,#08H ;Offset from table start MOV DPTR,#01F00H ;Table start address MOVC A,@A+DPTR ;Gets target value from the table ;start address + offset and puts it ;in A. After the execution of the above instructions, the program will branch to address 1F08H (1F00H+08H) and transfer into the accumulator the data In 8051 there are different ways in which you can address or use these instructions. These are called addressing modes. Immediate addressing mode. In this addressing mode, the data is specified in the instruction itself. The # symbol specifies the value being data. E.g. MOV A, #35H (Value 35 is moved in Accumulator). 8051 Instruction Set - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. 8051 controller instruction set 8051 microcontroller RAM and ROM memory space can be expanded by adding external memory chips. These external memory addresses are always accessed by using Indirect Instruction MOVX @ Rp MOVX @ DPTR MOVC A, @A+ DPTR MOVC A, @A+ PC. MOVX A, @Rp ;copy the contents of the external address in Rp to A The looping operation is used for running the same set of subroutine inside a program number of times as per the requirement. Consider the instruction DJNZ register; label is used for performing a loop operation. In this instruction, the register is decremented by 1; if this is not zero, then 8051 jumps to the target address referred by the label. THE 8051 INSTRUCTION SET All commands in alphabetic order: ACALL addr11 DIV AB LJMP addr16 RETI ADD A, MySpace
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