Wed, 9th Dec 2015, 19:58 Re: The Supervisor Stack -- Very important error in the textbook

A student writes:

> Hello Dr. Patt,
> I'm studying for the EE 306 final right now and I noticed something about
> the book's explanations for interrupts. On page 263 in Chapter 10, an
> example of the Supervisor Stack is shown, and it shows the PSR being pushed
> on top of the PC (meaning that the PC gets pushed first, followed by the
> PSR).
> However, appendix C shows that the PSR gets pushed first, followed by the
> PC. A question on the 2009 Final Exam also shows that, in the stack, the PC
> is stored in the memory location preceding the location in which the PSR is
> stored, meaning that the PC is at the top of the stack. The state machine
> also shows the PSR being pushed first, followed by the PC.
> Does Chapter 10 contain an error or is there something else that I'm
> missing?
> Thanks,
> <<name withheld to protect the student who sees an inconsistency>>

Have you checked the errata on the McGraw-Hill web site.  I thought we
corrected that error a long time ago.

In any case, the CORRECT sequence is: first push PSR, then push PC.

I should also remind you that any time you see an error in the book, you
should always check the errata page on the McGrwa-Hill web site.  You can
get there from my home page.  See the discussion on 306 in the list of topics
near the top of my website.

Good luck preparing for the final exam.

Yale Patt