10/26/2006

A student writes:

        Dr. Patt,

        I was looking in the back of the book on page 528 
        at the assembler format
        for the branch instruction and I was wondering what one of the formats
        meant.  It is the one with the small cross next to the BR.  
        By process of elimination, I would guess that it is BR check none 
        of the condition codes.  Is that right or does it mean something 
        different?  Thank you for your time.

        <<name withheld to protect one who may be weak on attendance>>

Two reasons for sharing this with the rest of the class.

First, the question itself.  For those of you who come to class, you may
recall I specifically answered that in class.  Was this guy in class, and
if so, was he listening to music or sleeping.  I sent him a private email
message asking him those questions.

Second, is this something he needed to ask me, or is there a quick way he 
could have found out for himself.  At this point, from the TA discussion 
sections, you should all be familiar with the LC-3 Simulator and the 
Assembler and Debugger that are part of it.  One could write a very small 
program:

                .ORIG   x3000
                BR      HERE
        HERE    TRAP x25
                .END

and assemble it.  ...and then look at what is in location x3000.
The answer to his question appears.         

Good luck to those who still have not finished the program, and good
luck finishing successfully EE 306.

Yale Patt