Data transfers

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We have 32 General purpose register (r0 - r31)

Mnemonic	Description
ldi	load immediate
mov	copy register
movw	copy register pair

::ldi

ldi is part of a special set of immediate instructions. Immediate instructions operate on a register and require a constant be supplied as an operand. Immediate instructions are very useful as they allow you to operate with a number you supply in the code itself.

ldi   r16, 85   ; load 85 into register 16 (decimal)

ldi   r16, $55   ; load 85 into register 16 (also hex)

ldi   r16, 0x55   ; load 85 into register 16 (hex)

ldi   r16, 0125   ; load 85 into register 16 (octal)

ldi   r16, 0b01010101   ; load 85 into register 16 (binary)

⚠️ REMINDER
Immediate instructions only work with registers 16 through 31. Trying to use them with registers 0 through 15 will result in an error.

::mov

The contents of one register can be copied to another register using the mov instruction. Since ldi only works on registers 16 through 31, the mov instruction is a useful way to load a constant into one of the lower 16 registers.

ldi   r16, 0x55   ; load 0x55 to r16
mov   r0, r16   ; copy content of r16 to r0

⚠️ REMINDER
It only copies the contents to first arg, but second arg remain unchanged.

::movw

This allows us to operate on 16-Bit values. Allows to copy the contents of one register pair into another pair.

ldi   r16, 0x34   ; load lower byte of 0x5734 into r16
ldi   r17, 0x57   ; load upper byte of 0x5734 into r17

movw    r1:r0, r17:r16   ; copy contents of r17 to r1; r16 to r0 

Instead of typing all pair, just write lower byte register, it knows what have to do. :D

movw    r0, r16   ; copy contents of r17 to r1; r16 to r0

⚠️ REMINDER
Lower Byte Register should be EVEN! ( 0,2, ...)

⚠️ REMINDER
Source registers will be remain unchanged!!!

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