; thats how i understood the instructions
; after reading a few short avr tutorials
; hope it helps

.include "m64def.inc"
    jmp RESET

.dseg
var1: .BYTE 3 ; high byte of the word
var2: .BYTE 2 ; low byte  of the word - i hope thats correct


.cseg
const: .DB 0xAA, 0xCC, 0xDD

reset:
    ldi ZL, low(var1)
    ldi ZH, high(var1)     ; load high byte of address in Z pointer: Z = &var1
    ldi r17, 0xBB          ; r17 = 0xBB
    st Z, r17              ; *Z = 0xBB: var1 = 0xBB
    ldi ZL, low(const<<1)
    ldi ZH, high(const<<1) ; load low byte of address in Z pointer: Z = (&const) + 1: points on 0xCC
    lpm                    ; load r0 = *Z: r0 = 0xCC
    jmp mainloop
.dseg
var3: .BYTE 4
.cseg
.org 0x20
mainloop:
    ldi r20, 0xF0         ; r20 = 0xF0
    ...

Symbol    Segment   Value
var1      dseg            ?
var3      dseg            ?
reset     cseg            ?
const     cseg            ?
mainloop  cseg            ?