Help with swapping every two bits

[lios1984]

I have a problem with creating a loop that swaps every two bits. The general idea is this (without loops):

JMP START
N: equ 8
Data1:  DB 03h, 23h, N, 34h, 2Bh, 6Fh, 8AEh, 24h, 1EAh


START:  LDA N
    MOV D, A


    LDA $4203h
    MOV B, A
    LDA $4204h
    STA $4203H
    MOV A, B
    STA $4204h

    LDA $4206h
    MOV B, A
    LDA $4207h
    STA $4206H
    MOV A, B
    STA $4207h

    LDA $4208h
    MOV B, A
    LDA $4209h
    STA $4208H
    MOV A, B
    STA $4209h

    LDA $420Ah
    MOV B, A
    LDA $420Bh
    STA $420AH
    MOV A, B
    STA $420Bh


END:    HLT

How I can use loop and counters with this code? This is my first week on Asselmbly but I have worked previously on programming.