Swaps content of EBX as follows:

Requirement: Store $\text{'}$A$\text{'}$ in EBX LSB or BL$,$ store $\text{'}$B$\text{'}$ in BH$,$ and then swap BL and BH$.$ You will have to use a temporary storage, you can use EAX $($use AL$)$ or any storage you may define.