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'Myke's book, a freshman's comment.'
1998\11\15@112114 by Stig Brautaset

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Got the book yesterday, and my only complaint so far is that the
plastic-envelope in the back was glued with the opening facing the cover, so
I had to rip it off in order to get out the discette.

However, I have some questions. I do not understand the purpose of address
banks. Why are they there? Why are the same registers except of TRIS and
OPTION listed in both (or all four) banks? Is it due to a hardware
limitation, or is it just to give us PIC freshmen a hard time figuring out
how to use it?

Stig

=====================================================
Stig Brautaset  -  spam_OUTsbrautasTakeThisOuTspamc2i.net  -  ICQ: 11052183
Student of electronics - http://home.c2i.net/sbrautas
=====================================================

1998\11\15@224110 by paulb

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Stig Brautaset wrote:

> However, I have some questions. I do not understand the purpose of
> address banks.  Why are they there?

 To allow addressing of registers with fewer address bits, since the
opcode width is essentially limited.  Like bank switching 8-bit CPUs to
access greater than 64k byte memory.

> Why are the same registers except of TRIS and OPTION listed in both
> (or all four) banks? Is it due to a hardware limitation,

 To some extent, as you imply, it simplifies address decoding.  Mainly
it is to make important registers available independently of bank
switching.  Important registers (such as Status), and some RAM to be
used for the more important storage, appear in all banks to make them
readily accessible, while less "important" registers and RAM are in
banks to save on address width.

> or is it just to give us PIC freshmen a hard time figuring out how to
> use it?

 So goes one theory...  A bit like the "Irish cornflakes packet" with
"open other end" on both ends.
--
 Cheers,
       Paul B.

1998\11\16@122916 by myke predko

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Hi Stig,

>Got the book yesterday, and my only complaint so far is that the
>plastic-envelope in the back was glued with the opening facing the cover, so
>I had to rip it off in order to get out the discette.

Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
about it.

>However, I have some questions. I do not understand the purpose of address
>banks. Why are they there? Why are the same registers except of TRIS and
>OPTION listed in both (or all four) banks? Is it due to a hardware
>limitation, or is it just to give us PIC freshmen a hard time figuring out
>how to use it?

The address banks are there because as Microchip originally laid out the
instructions, there was only seven bits available for register addressing.
(six bits for the instruction, one bit for the destination, which leaves
seven bits).  These seven bits can only allow access to 128 register
addresses.

The solution to this was to create a number of 128 address "banks", which
could provide additional memory and registers to the application.  To access
these banks, the "RPx" bits in the STATUS register have to be set.

In the original PICMicros (the 16C5x or "low-end" devices), the only
peripherals were the Timer (TMR0) and I/O pins.  To control the driving
characteristic of the I/O pins, the "TRIS" and "OPTION" instructions were
used.  The problem with these instructions is that the application cannot
read back their contents.  When the "mid-range" parts were designed, the
"TRIS" and "OPTION" registers were put into the I/O map.  To maintain
source-code level compatibility with the previous devices, these registers
were placed in Bank1, where "superset" code would access them.

The common registers (INDF, FSR, STATUS and INTCON) are in each bank to
allow them to be accessed no matter where the application is running.  In
some cases, it makes it very convenient (and, if the STATUS register wasn't
in all the banks, then it would be impossible to return to Bank 0).


The designers of the PICMicro were very fanatical in their zeal to make sure
that all instructions would only take up one instruction word and no more.
This criteria puts a few restrictions on how data and instructions are
accessed in the PICMicro and resulted in an architecture that when you first
see it, you're left scratching your head.

Good luck and let me know how you make out with the book,

myke

John Douglas and Mark Olshaker explore the minds of some of the most
dangerous criminals of our time; "Obsession" is this week's book at:

http://www.myke.com/Book_Room/book1a.htm

Also look at:

http://www.myke.com/My_Books/homcu.htm

for information on "Handbook of Microcontrollers" which has been named the
Main Selection for November 1998 for the Electronics Book Club!

1998\11\16@175618 by Eduardo R.

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>Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
>about it.
>

Certainly ....Yes, same with my copy but  I unglued the top and the pocket
still in place.



>Hi Stig,
>
>>Got the book yesterday, and my only complaint so far is that the
>>plastic-envelope in the back was glued with the opening facing the cover, so
>>I had to rip it off in order to get out the discette.
>

1998\11\17@051124 by cousens

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myke predko wrote:
>
> Hi Stig,
>
> >Got the book yesterday, and my only complaint so far is that the
> >plastic-envelope in the back was glued with the opening facing the cover, so
> >I had to rip it off in order to get out the discette.
>
> Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
> about it.

I too damaged my copy when removing the disk.

Good luck in your discusions with them, I can't see that they would give
a
shit though, there only concern would be to make it as hard as posible
for someone to steal before buying

One of my worst hates are the stickers they put all over cd cases.
I now say to the shop that it is a gift and will they remove the
sticker for me, the manager usually gives me a replacement case

--
Peter Cousens
email: .....cousensKILLspamspam@spam@her.forthnet.gr  phone: + 3081 380534
snailmail:  Folia, Agia Fotini, Karteros, Heraklion  Crete, Greece.

We cannot blame God for creating a World with so many problems,
He had just upgraded from win3.11 to win95.
No wonder Eve recommended Apple.

1998\11\17@092702 by Felix Sawicki

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Myke, it looks like the envelope opening faces the back cover on purpose
and with good reason.  The envelope is not sealed like most, but has
about a 1/8 inch open slot across it.  If the slot wasn't facing the
cover, the diskette would fall out fairly easily (or get swiped in the
book store). It does pull up some of the surface of the back cover when
you remove it, but it's no big deal.

Felix

{Quote hidden}

1998\11\17@120317 by John Payson

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>Got the book yesterday, and my only complaint so far is that the
>plastic-envelope in the back was glued with the opening facing the cover, so
>I had to rip it off in order to get out the discette.

|Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
|about it.

I think the book is set up like this to ensure that the disk
doesn't come out to easily, either in transit or into the hands
of a thief.

I think a better approach might be to have a perforated section
on the last page, to which the envelope might be attached.  If
the equipment at MgH was set up suitably, the "envelope" could
even be made from that same sheet.  Alternatively, since many
books have cover flaps on them, perhaps the rear cover of the
book could include a tear-off flap to which the diskette env-
elope could be affixed.

BTW, speaking of damage to items when removing them from packing,
my fiancee/wife ordered a CD copy of a radio broadcast (legit); it
was on two of those "blue" recordable CD's (as opposed to the gold
ones).  Unfortunately, the plastic envelope they came in was a bit
tacky and removing the disk caused large parts of it to come delam-
inated.  Experimenting with other "blue" CD's indicates that the
back sides of them are quite fragile, and that even small scratches
can quickly grow so as to render an entire disk useless.

Back to PICs: why can't they make CD's as indestructible as PICs?
Now *THOSE* things will take a beating and keep right on going...
Though I do have a beef with the 16C924/JW parts: when placed into
sockets, the corner pins on those parts often short together.  I
don't think that would normally be a problem when parts are soldered
onto a board, but since /JW parts are normally used in sockets, I
wonder if there'd be some way to make the legs less prone to shorting?

1998\11\17@134400 by Rj.Moore

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> > >Got the book yesterday, and my only complaint so far is that the
> > >plastic-envelope in the back was glued with the opening facing
> > the cover, so I had to rip it off in order to get out the discette.
> >
> > Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
> > about it.
>
> I too damaged my copy when removing the disk.

I'm pretty sure the sleeve was placed that way on purpose to prevent
the diskette from falling out.  This isn't one of those sleeves that
require the user to cut a slot into it, after all.

I didn't have any problem, though, in just peeling back the top section
from its loose, gummy adhesive.

rj

1998\11\18@012137 by Alessandro Zummo

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Il 17-Nov-98, Eduardo R. scrisse:


>> Has anybody else seen this?  If it's a problem, I'll talk to McGraw-Hill
>> about it.
>>
> Certainly ....Yes, same with my copy but  I unglued the top and the pocket
> still in place.

>> Hi Stig,

>>> Got the book yesterday, and my only complaint so far is that the
>>> plastic-envelope in the back was glued with the opening facing the cover,
>>> so I had to rip it off in order to get out the discette.

me too.

--

  - *Alex* -

 http://freepage.logicom.it/azummo/

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