Skip to main content

Data Transfer Group Instructions (Part-IV)

By
LDAX Rp:
  • This instruction copies the contents of memory location to the accumulator.
  • The address of the memory location is not given in the instruction directly.
  • The address of the memory location is given by Rp register pair.
  • The register pair can be BC or DE only.
  • Only high order register is specified for register pair.
  • No flags are affected.
  • It is a one byte instruction.
  • Indirect addressing mode is used.
Example:
If BC = 2000H and (2000H) = 30H
LDAX B ; This instruction loads the contents of memory location 2000H i.e. 30H into A.

If DE = 4200H and (4200H) = A4H
LDAX D ; This instruction loads the contents of memory location 4200H i.e. A4H into A.

STAX Rp: 
  • This instruction copies the contents of accumulator to the memory location.
  • The address of the memory location is not given in the instruction directly.
  • The address of the memory location is given by Rp register pair.
  • The register pair can be BC or DE only.
  • Only high order register is specified for register pair.
  • No flags are affected.
  • It is a one byte instruction.
  • Indirect addressing mode is used.
Example:
If BC = 3000H and A = 80H
STAX B ; This instruction copies the contents of A i.e. 80H to the memory location 3000H.

If DE = 2100H and A = 54H
STAX D ; This instruction copies the contents of A i.e. 54H to the memory location 2100H.

XCHG:
  • This instruction exchanges the contents of H register with D register and L register with E register.
  • No flags are affected.
  • It is a one byte instruction.
  • Register addressing mode is used.
Example:
If DE = 2040H and HL = 2141H
XCHG ; This instruction loads the data as follows: H = 20H, L= 40H, D = 21H and E = 41H.
Labels:

Comments

Post a Comment

Popular posts from this blog

Logical Group Instructions (Part-VI) - RLC, RRC, RAL, RAR

By
RLC: This instruction rotates the contents of accumulator to the left by one bit. It will shift B0 to B1, B1 to B2,............B7 to B0 as well as to carry flag . Only CY flag is modified. It is a one byte instruction. Implied addressing mode is used. Before execution: After execution: Example: If A = 0101 0111 = 57H and CY = 1 RLC ; Now A = 10101110 = AEH and CY = 0. RRC: This instruction rotates the contents of accumulator to the right by one bit. It will shift B7 to B6, B6 to B5,............B0 to B7 as well as to carry flag. Only CY flag is modified. It is a one byte instruction. Implied addressing mode is used. Before execution: After execution: Example: If A = 1001 1010 = 9AH and CY = 1 RLC ; Now A = 0100 1101 = 4DH and CY = 0. RAL: This instruction rotates the contents of accumulator to the left by one bit along with the carry . It will shift B0 to B1, B1 to B2,............B7 to CY and CY to B0 . Only CY flag is modifi...
Post a Comment
Read more

Program to pack the two unpacked BCD numbers

By
Statement: Pack the two unpacked BCD numbers stored in memory locations 2000H and 2001H and store the result in memory location 2002H. The least significant digit is stored at 2000H. Example: (2000H) = 04H (2001H) = 09H Result = (2002H) = 94H Program: LDA 2001H                        ; Obtain the most significant BCD digit RLC                                    ; Rotate left  RLC                                    ; Rotate left  RLC                                    ; Rotate left  RLC                                    ; Rotate left...
Post a Comment
Read more

Program to exchange the contents of two memory locations

By
Statement: Exchange the contents of memory locations 2000H and 2001H. Example:  Initially, (2000H) = 34H (2001H) = 20H After exchanging, (2000H) = 20H (2001H) = 34H Program 1 using direct addressing instructions: LDA 2000H               ; Get the contents of location 2000H into accumulator MOV B, A                  ; Move the contents of accumulator into register B LDA 2001H                ; Get the contents of location 2001H into accumulator STA 2000H                 ; Store the contents of accumulator into location 2000H MOV A, B                  ; Move the contents of register B into accumulator STA 2001H                 ; Store the contents of accumulator into location 2001H HLT  ...
Post a Comment
Read more