What is a vector file?

What is a vector file?

[Home Email]

In studying a boot prom for an Hitachi SH032 along
with the source code, I am beginning to get a good
understanding of how the GNU AS, LD works. However,
when I read in the boot prom I have into my programmer
I find locations 0x0000 - 0x01C7 filled with various
hex numbers that I don't know what they are.  I do
know my code begins at 0x01C8.   While studying the
source code I believe that what I have at the 
beginning of the boot prom is something generated by 
this one source file called Vectors.S.  But what is
this file?  It seems as though it is setting up the
Hitachi microcontroller before it begins executing
code.  Here is some sections of this vector.S file...

/*----------------------------------------------------
FILE NAME:
  Vectors.S
FUNCTION:
  This file contains the vectory overlay for the
SH7000
  microcontroller.
ROUTINES:
NOTES:
  This file references 2 other interrupt handlers
  1. _start - entry point of program
  2. _interruptDispatch - for soft vectoring all the
other interrupts
----------------------------------------------------*/

/* ...Global Variables:
*/

  .extern ShTest
  .extern _interruptDispatchRsv
  .extern _interruptDispatch4
  .extern _interruptDispatch6

...this continues down for many many lines of this
stuff
....and then I see this....

  .extern _stack

/* ...Local Variables:
*/

/* ...Routines:
*/
  .section VECTORS
  .globl _vectors

_vectors:
 .int  ShTest       ! 000-003 0  Power up Reset Vector
 .int  _stack       ! 004-007 1  Power Up Stack
 .int  ShTest       ! 008-00B 2  Manual Reset Vector
 .int  _stack       ! 00C-00F 3  Manual Reset Stack
 .int  _interruptDispatch4      ! 010-013 4  Invalid
Instruction
 .int  _interruptDispatchRsv     ! 014-017 5  Reserved
 .int  _interruptDispatch6    ! 018-01B 6  Invalid
Slot Instruction
 .int  _interruptDispatchRsv     ! 01C-01F 7  Reserved
 .int  _interruptDispatchRsv     ! 020-023 8  Reserved
 .int  _interruptDispatch9  ! 024-027 9  CPU bus error

....this continues on down and finally ends with
this..

 .int  _interruptDispatchRsv     ! 1BC-1BF 111 A/D 
Reserved

/* ...Watch Dog Timer
*/
 .int  _interruptDispatch112       ! 1C0-1C3 112 WDT

/* ...Refresh Control
*/
 .int  _interruptDispatch113         ! 1C4-1C7 113 REF

 .end

I am but just a learner here so bear with me while I
ask some dumb questions.....

It looks as though as soon as the microcontroller
begins it is initalizing itself.  Is this what the
vector file is for?
Do all embedded microcontrollers use a file like this
at the beginning of their their boot prom and how much
intialization is necessary?
Is there any documentation about vector files and how
to use them (or other methods)?

Thanks for any help on this.

R.Floyd










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Re: What is a vector file?

[Keith Wright]

> From: Home Email <home_email2000@yahoo.com>
> 
> In studying a boot prom for an Hitachi SH032 along
> with the source code, I am beginning to get a good
> understanding of how the GNU AS, LD works. However,
> when I read in the boot prom I have into my programmer
> I find locations 0x0000 - 0x01C7 filled with various
> hex numbers that I don't know what they are.

Clearly, you are out of your depth, but you may be
swimming in a minute.  You need to learn about the
hardware you are running on.  Go to Hitachi and ask
for the SH032 "Principles of Operation", "Programmer's
Reference", or "Instruction Set List".  I don't
know what it's called by Hitachi, and I don't have it,
so don't ask me more about that.  Some general book
on programming microprocessors may also be helpful.

> FILE NAME:
>   Vectors.S
> FUNCTION:
>   This file contains the vector overlay for the
>   SH7000  microcontroller.

... so on.  Much more than we need to see of the
interrupt vector table.  Go learn what an interrupt
vector table is, the comment says all that could be
said, you need to learn the language it is written in.

> I am but just a learner here so bear with me while I
> ask some dumb questions.....

I'm being as polite as I can, given my abrasive personality.

> It looks as though as soon as the microcontroller
> begins it is initalizing itself.  Is this what the
> vector file is for?

Its a list of addresses to jump to when an interrupt
happens.  Different addresses for different interrupts.
One interrupt is Power-on and Reset.

> Do all embedded microcontrollers use a file like this
> at the beginning of their their boot prom

You could imagine doing it in other ways, but _every_
boot prom does it somehow, whether it is embeded in
a can opener or largest Supercomputer of the week.

> and how much intialization is necessary?

See processor reference and motherboard schematic.

> Is there any documentation about vector files and how
> to use them (or other methods)?

CS 201, Undergraduate Intro to Computer Architecture.

> Thanks for any help on this.

De nada.

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Re: What is a vector file?

[Michael Schwingen]

On Sun, Oct 22, 2000 at 09:29:43AM -0700, Home Email wrote:
> It looks as though as soon as the microcontroller
> begins it is initalizing itself.  Is this what the
> vector file is for?

It contains various exception vectors, which are located at the beginning of
the ROM for the SH.

Look up the chapter on exception handling in the SH manual - you will then
get an impression why these vectors are needed. After that, this method of
creating them will become more clear.

> Do all embedded microcontrollers use a file like this
> at the beginning of their their boot prom and how much

No. It depends on the CPU where exception vectors are placed - the 68k
family has only the reset vector/stack fixed at address 0 and 4, the rest
may be relocated. Other CPUs use fixed locations at the end of memory.

Only the reset vector is needed at a fixed location - the rest depends on
the memory map of your hardware - for a system where the exception vectors
are placed in RAM, you will have to initialize them by some other way in
your startup code.

cu
Michael

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Re: What is a vector file?

[Home Email]

In the last five hours since I wrote this I have done
nothing read, read, read GNU AS,LD and Hitachi manual.
 I understand now what is going on and how this is
working.  It's slowly coming together for me.

Thanks for your response.

R.F.


--- Keith Wright <kwright@gis.net> wrote:
> > From: Home Email <home_email2000@yahoo.com>
> > 
> > In studying a boot prom for an Hitachi SH032 along
> > with the source code, I am beginning to get a good
> > understanding of how the GNU AS, LD works.
> However,
> > when I read in the boot prom I have into my
> programmer
> > I find locations 0x0000 - 0x01C7 filled with
> various
> > hex numbers that I don't know what they are.
> 
> Clearly, you are out of your depth, but you may be
> swimming in a minute.  You need to learn about the
> hardware you are running on.  Go to Hitachi and ask
> for the SH032 "Principles of Operation",
> "Programmer's
> Reference", or "Instruction Set List".  I don't
> know what it's called by Hitachi, and I don't have
> it,
> so don't ask me more about that.  Some general book
> on programming microprocessors may also be helpful.
> 
> > FILE NAME:
> >   Vectors.S
> > FUNCTION:
> >   This file contains the vector overlay for the
> >   SH7000  microcontroller.
> 
> ... so on.  Much more than we need to see of the
> interrupt vector table.  Go learn what an interrupt
> vector table is, the comment says all that could be
> said, you need to learn the language it is written
> in.
> 
> > I am but just a learner here so bear with me while
> I
> > ask some dumb questions.....
> 
> I'm being as polite as I can, given my abrasive
> personality.
> 
> > It looks as though as soon as the microcontroller
> > begins it is initalizing itself.  Is this what the
> > vector file is for?
> 
> Its a list of addresses to jump to when an interrupt
> happens.  Different addresses for different
> interrupts.
> One interrupt is Power-on and Reset.
> 
> > Do all embedded microcontrollers use a file like
> this
> > at the beginning of their their boot prom
> 
> You could imagine doing it in other ways, but
> _every_
> boot prom does it somehow, whether it is embeded in
> a can opener or largest Supercomputer of the week.
> 
> > and how much intialization is necessary?
> 
> See processor reference and motherboard schematic.
> 
> > Is there any documentation about vector files and
> how
> > to use them (or other methods)?
> 
> CS 201, Undergraduate Intro to Computer
> Architecture.
> 
> > Thanks for any help on this.
> 
> De nada.
> 
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> Want more information?  See the CrossGCC FAQ,
> http://www.objsw.com/CrossGCC/
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> 


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