Re:Re: high byte of address question

Thread View: net.micro.mac

1 messages

[T] Back to Threads [V] Tree View [G] Group Articles

1 total messages Started by edmoy Sat, 19 Jan 1985 21:10

#415

Author: edmoy
Date: Sat, 19 Jan 1985 21:10

19 lines
1391 bytes

>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

Thread Navigation

This is a paginated view of messages in the thread with full content displayed inline.

Messages are displayed in chronological order, with the original post highlighted in green.

Use pagination controls to navigate through all messages in large threads.

Back to All Threads