Lpc2000

Hi folks,

I hope this question isn't inaapropriate for such a group, but I'm new
to the ARM. Even though I've programmed a fair array pf eight and
sixteen bit devices in the past, I don't ever remember dealing with a
device that has a supervisor mode. As far as I understand it,
supervisor mode, user mode etc are for when you are running an
operating system. Therefore, if I write "normal" run-'til-complete
type software, does that mean that I can (or maybe should) just put
the device in supervisor mode on boot up and forget about it?

If this is an FAQ type question for ARM users and someone knows of a
useful document to explain this sort of thing I'd be most happy to go
and read it if they'd be kind enough to point me in the right direction! 

Many thanks,

Rob.

--- In lpc2000@yahoogroups.com, "dibosco" <robert.wood@a...> wrote:
> Hi folks,
> 
> I hope this question isn't inaapropriate for such a group, but I'm 
new
> to the ARM. Even though I've programmed a fair array pf eight and
> sixteen bit devices in the past, I don't ever remember dealing with 
a
> device that has a supervisor mode. As far as I understand it,
> supervisor mode, user mode etc are for when you are running an
> operating system. Therefore, if I write "normal" run-'til-complete
> type software, does that mean that I can (or maybe should) just put
> the device in supervisor mode on boot up and forget about it?
> 
> If this is an FAQ type question for ARM users and someone knows of a
> useful document to explain this sort of thing I'd be most happy to 
go
> and read it if they'd be kind enough to point me in the right 
direction! 

ARM has something on this:

http://www.arm.com/support/faqdev/1320.html

I think that most of the C development toolsets will default to 
Supervisor mode when you run code developed with them. You will have 
to explicitly switch to User mode in your software if you require it. 
This is definitely the case with the GNU tools, otherwise none of the 
program examples which do things like flash LEDs wouldn't work.

Leon

Rob

I think you have a reasonably good understanding of this. 
The only problem with using supervisor mode is that this is the mode used for 
SWi, so if you're using SWI then running in system/user mode is prefered.

The reason this is an issue is that the ARM has banked registers, with 
various registers banked for various modes. If you're using exceptions (SWI, 
interrupts,...) then you don't want them stomping on your main thread of 
execution.

-- CHarles

On Thursday 22 April 2004 07:39, you wrote:
> Hi folks,
>
> I hope this question isn't inaapropriate for such a group, but I'm new
> to the ARM. Even though I've programmed a fair array pf eight and
> sixteen bit devices in the past, I don't ever remember dealing with a
> device that has a supervisor mode. As far as I understand it,
> supervisor mode, user mode etc are for when you are running an
> operating system. Therefore, if I write "normal" run-'til-complete
> type software, does that mean that I can (or maybe should) just put
> the device in supervisor mode on boot up and forget about it?
>
> If this is an FAQ type question for ARM users and someone knows of a
> useful document to explain this sort of thing I'd be most happy to go
> and read it if they'd be kind enough to point me in the right direction!
>
> Many thanks,
>
> Rob.
>

At 15:39 2004-04-21, you wrote:
>If this is an FAQ type question for ARM users and someone knows of a
>useful document to explain this sort of thing I'd be most happy to go
>and read it if they'd be kind enough to point me in the right direction!
>
>Many thanks,
>
>Rob.

http://www.altera.com/literature/third-party/ddi0100e_arm_arm.pdf
http://www.atmel.com/dyn/resources/prod_documents/doc0673.pdf
http://www.arm.com/miscPDFs/4718.pdf
http://www.ra.informatik.uni-stuttgart.de/~ghermanv/Lehre/SOC02/
http://tisu.mit.jyu.fi/embedded/TIE345/luentokalvot/Embedded_3_ARM.pdf