Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!necntc!ima!cfisun!palladium!nw From: nw@palladium.UUCP (Neil Webber) Newsgroups: comp.sys.m68k Subject: ADDA.L (SP)+,SP (68020) Message-ID: <407@palladium.UUCP> Date: Mon, 30-Nov-87 12:10:24 EST Article-I.D.: palladiu.407 Posted: Mon Nov 30 12:10:24 1987 Date-Received: Sat, 5-Dec-87 02:46:20 EST Organization: Epoch Systems, Marlboro MA Lines: 29 Keywords: MC68020 Is the following instruction sequence an "undefined" operation? ADDA.L (SP)+,SP The intent is to add the value at the top of the stack, plus 4, to the stack pointer. I've tried it, and it works, but I'm wondering if Motorola prefers to consider this "undefined" operation. The closest thing I can find to a discussion of this is under MOVES, where it says (p B-117, 68020 User's Manual, Second Edition): MOVES.x An,(An)+ or MOVES.x An,-(An) where An is the same address register for both source and destination operand is an undefined operation. Is this meant to be a generic warning or only for MOVES? By the way, if someone from Motorola is reading this article, you should note that the actual wording in the book is quite mangled ... it needs correction. Thanks in advance. -- Neil Webber / Epoch Systems, Marlboro MA / (617) 481-3717 {harvard!cfisun, linus!alliant}!palladium!nw