Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 v7 ucbopal-1.9 BSD 4.2; site ucbopal.CC.Berkeley.ARPA Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!ucbvax!ucbtopaz!ucbopal!edmoy From: edmoy@ucbopal.CC.Berkeley.ARPA Newsgroups: net.micro.mac Subject: Re:Re: high byte of address question Message-ID: <228@ucbopal.CC.Berkeley.ARPA> Date: Sat, 19-Jan-85 16:10:13 EST Article-I.D.: ucbopal.228 Posted: Sat Jan 19 16:10:13 1985 Date-Received: Mon, 21-Jan-85 02:28:51 EST Organization: Univ. of Calif., Berkeley CA USA Lines: 19 >The reason the high byte gets trashed in SumacC code has nothing to do >with the Mac hardware, but instead is a side-effect of the Sumacc >relocation scheme. You are quite correct about sumacc method, which I am aware of. My question had to do with the 68000 Load Effective Address (lea) instruction itself. When I wrote some assembly language code to support my C code, it seemed that the lea instruction itself was putting something in the high byte. So after I did a lea to an address register and then moved it to a data register, I found I had to clear the high byte to use it the way I wanted or otherwise the high byte would screw things up. Edward Moy Computing Services University of California Berkeley, CA 94720 edmoy@ucbopal.ARPA ucbvax!ucbopal!edmoy