01 LDI

LDI

• The LDI (Load Immediate) instruction is designed to quickly load a constant value (K) into a General Purpose Register (GPR) within a specific range.

Instruction Syntax

LDI Rd, K

• Rd: The destination register where the constant value $K$ will be stored.
  • Must be one of the upper 16 registers: R16–R31.
• K: The immediate value to be loaded into Rd.
  • Must be an 8-bit constant value.
  • Range: (Values outside this range will result in an error.)
    • Decimal: $0-255$
    • Hexadecimal: $0x00-0xFF$
    • Binary: $0b000000000–0b11111111$

Examples

Valid Instruction:

LDI R20, 0x25

• R20: R20 is in the valid register range R16–R31.
• K: 0x25 (37 in decimal) is within the valid range for K.
• Effect: Load 0x25 into R20.

Valid Instruction:

LDI R20, 25

• R20: R20 is valid.
• K: 25 is within the range 0–255.
• Effect: Load 25 (decimal) into R20.

Error Example:

LDI R10, 0x10

• R10: R10 is not in the valid register range R16–R31.
• Result: Error.

Error Example:

LDI R25, 0x200

• R25: R25 is valid.
• K: 0x200 (512 in decimal) exceeds the 8-bit range (0–255).
• Result: Error.