Hello, I stumbled across a problem lately, and this thread http://www.keil.com/forum/docs/thread2344.asp helped me find a solution. Let me quote Gilles: Don't apply conditonal compilation at the %define but at the init of the ADDSEL (the last %define always win !)(bug sent to KEIL few months ago) (Dated 2/12/03) I would like to know if there really is a problem with the Keil assembler, or would this sort of issue only be a side effect of some macro expander subtlety? Can anyone elaborate on this? Rgds, Steph-