I have one also that I see every now and then but here it is. [mov R24Z4 D1638]. from what I read above the Z4 address would be a small adress number change for r24 almost like a correction. Start at R24 and remove or add a few to it's address. The mov function I know is moving something into d1638. My understatang now is that mov contents of either r20, r22,r28 or somewhere in there depending on the value of z4 into d1638. If that is true that z is like an address modifier.