Re: EE 360N: Questions about Lab2
A student writes,
I have a couple questions pertaining to this lab:
I will try to deal with some of this, but I will leave most of it to
my TAs. I am in Phoenix and just got out of a panel I was on, and
have logged in via a pretty horrible connection.
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2. In between executing different instructions,
the condition codes aren't
cleared, correct? Meaning, if an instruction does not alter
the CC, are the CC values from the previous instruction kept the same?
Absolutely! And that is in fact at the heart of the ISA. That is, seven
instructions set condition codes. The others don't touch them. Branches,
of course, use them. This is consistent with all ISA, by the way, not just
3. Under the section "Important" on the Lab2 instructions, the JSR(R)
instruction definition has been changed. The original Appendix A definition has
the incremented PC stored into R7. The changed instructions put PC into a temp
variable, and then assign R7 the value of the temp variable.
a. Is there a reason why we're to use a temp variable instead
of directly assigning the PC to R7?
Yes! AND, I thought I asked you to tell me the reason on the next
problem set. I will certainly tell you the reason after it is turned
in, but want you to take a crack at it first.
b. Although not indicated in the
updated JSR(R) instruction definition, R7
should still contain the value of the incremented PC, right?
I thought my TAs had updated that.
<< name withheld >>