Data Transfer Instructions

• Used for moving data within the computer.
  • Register to Register.
  • Register to Memory.
  • Memory to Register.
  • Constant to Register (only works for r16-r31).
  • The ATmega32 cannot transfer directly from one Memory location to another Memory location.
• Does not affect flags

Register to Register

Copy Register

MOV Rd, Rr

• Moves (Copies) the value in register Rr to register Rd.
• Allows any register to be copied to any other register.
• Example: MOV r1, r10
  • R1 receives the value stored in in R10.

Memory to Register

Load Direct from SRAM

LDS Rd, K

• Loads (Copies) the value in memory location K into register Rd.
• Rd may be any register.
• K may be any address between 0 and 65535.
• This is known as Direct addressing.
• Often use a variable to represent the memory address.
• Example: LDS R1, Data
  • Data is a symbolic name of a memory location
  • R1 receives the value stored in the memory location Data.

Load Indirect

LD Rd, X

• Loads (Copies) the value in memory location stored in the X register (R27:R26) into register Rd.
• This is known as Indirect addressing.

Load Indirect and Post-Increment

LD Rd, X+

• Loads (Copies) the value in memory location stored in the X register (R27:R26) into register Rd and increments the value in the X register.
• X is incremented after the copy.
• This is called post-increment.

Load Indirect and Pre-Decrement

LD Rd, -X

• Decrements the value in the X register and loads (Copies) the value in memory location stored in the X register (R27:R26) into register Rd.
• X is decremented before the copy.
• This is called pre-decrement.

Note: Similar instructions exist for Y (R29:R28) and Z (R31:R30) registers.

Constant to Register

Load Immediate

LDI Rd, K

• Rd may be R16-R31
• K may be 0-255
• Loads (Copies) the value of K into register Rd.

Register to Memory

Store Direct to SRAM

STS K, Rr

• Stores (Copies) the value in register Rr into memory location k.
• Rr may be any register.
• K may be any address between 0 and 65535.
• This is similar to LDS.

Store Indirect and Variants

ST X, Rr

• Stores (Copies) the value in register Rr into the memory location stored in the X register (R27:R26).
• This is known as Indirect addressing.
• Post-increment and pre-decrement instructions similar to LD are available:
  • ST X+, Rr
  • ST -X, Rr
• Note: Similar instructions exist for Y (R29:R28) and Z (R31:R30) registers.