WRITE WORD - Write the given data to the address given

 Command:	$AF $02
 Data:		$ww $xx $yy $zz $qq $rr

 Write the word <$qqrr> to address <$wwxxyyzz>

 Command will be ACK'ed when received.
 Command ACK:	$00 $02
 Command DONE:	$1F $02