Tutorial Microcontroller MCS-51 ATMEL ISP

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Data Transfer

Internal RAM
Table 3 shows the menu of instructions that are available for moving data around within the internal memory spaces, and the addressing modes that can be used with each one. With a 12MHz clock, all of these instructions execute in either 1 or 2ms. The MOV <dest>, <src> instruction allows data to be transferred between any two internal RAM or SFR locations without going through the Accumulator. Remember, the Upper 128 bytes of data RAM can be accessed only by indirect addressing, and SFR space only by direct addressing.The Data Transfer instructions include a 16-bit MOV that can be used to initialize the Data Pointer (DPTR) for look-up tables in Program Memory, or for 16-bit external Data Memory accesses.

Table 1.4.3. MCS-51 Data Transfer Instruction

Mnemonic	Operation	Addressing Mode				Exect.
Mnemonic	Operation	Dir	Ind	Reg	Imm	Timer uS
Mov A,<src>	A=<src>	V	V	V	V	1
Mov <dest>,A	<dest>=A	V	V	V	V	1
Mov <dest>, <src>	<dest>=<src>	V	V	V	V	1
Mov DPTR,#data16	DPTR=16 bit immediate const	Accumulator Only				1
Push <src>	Inc SP	V	V	V		1
Pop <src>	Dec SP	Data Pointer Only				2
Xch A,<byte>	Acc and <byte> exchange data	Accumulator Only				1
Xchd A,@Ri	Acc and @Ri exchange low nibbles	V	V	V		1

;Lesson 1.4.1.

      Org 0h
Start:Mov A,#1    ; put 1 into the accumulator
      ADD A,#2    ; add the constant 2 to Accumulator (1+2)
      Mov 78h,#3  ; put 3 into internal RAM 78h
      ADD A, 78h  ; add Acc and RAM 78h content
      Mov R0, #79h; put 79 into R0
      Mov @R0, #4 ; put 4 into RAM 79h
      ADD A,@R0   ; add Acc and RAM 79h content
      Mov R5, #5  ; put 5 into R5
      ADD A,R5    ; add Acc and R5
      end

;Lesson 1.4.2.

      Org 0h
Start:Mov 78h,#34h ; [ 78h ] = 34h
      Mov 79h,#12h ; [ 79h ] =12h 
      Mov 7Ah,#0EFh; [ 7Ah ] = EFh
      Mov 7Bh,#12h ; [ 7Bh ] = 12h
      Mov A,78h    ; A = [ 78h ] 
      Add A,7Ah    ; A = A + [ 78h ]
      Mov 78h,A    ; [ 78h ] = A
      Mov A,79h    ; A = [ 79h ]
      ADDC A,7Bh   ; A = A + [ 7Bh ] + C 
      Mov 79h,A     ; [ 79h ] = A
      end

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