Search code examples
assemblybinaryavrinstructions

Assembly AVR Instruction LDI r22, 0x3D

Hi guys I'm trying to work out an AVR Instruction to machine code

LDI r22, 0x3D

LDI Rd, K 

1110 KKKK dddd KKKK

so far I've got 

1110 0011 dddd 1101

, how can dddd be covered in 4 bits if the maximum is 15.. ?

any help would be greatly appreciated.

Solution

  • LDI - Load Immediate

    Description: Loads an 8 bit constant directly to register 16 to 31.

    To encode a value of 16-31, you only need 4 bits (3-0) if you assume bit 4 to always be 1.

    In your case, the encoding would be;

    1110 0011 0110 1101 (where dddd is 6 since 16 + 6 = 22)