[fpc-devel] Arm Thumb2 - Stellaris status

[Geoffrey Barton]

On 20 Aug 2011, at 09:01, David Welch wrote:

> 
> Just jumping in here and maybe it was discussed but the cortex-m3 appears to have been designed so that if you match the arm abi you can put the address of handlers directly in the vector table and not have to trampoline off of a wrapper function.  basically 8 well chosen register are put on the stack so you dont have to preserve them, so that the handler has the look and feel of a standard function and not the look and feel of an interrupt handler.
> 
> I would not mix all cortex-m3 based devices into one definition.
> 
> Perhaps lumping all the stellaris parts into one but that would still get huge.  Maybe all the 800 series in one, all the 1000 series in another, and so on.  That is the way the vendors tend to manage information for their parts, and it makes sense as a sub-set of a larger family is very closely related and easier to manage the subtle differences.
> 
> Is it your intention to get all of the stellaris parts into this project all at once?  Or build some framework, add one or a few parts from each family and then over the course of time add a part or two here and there?
> 
> I would start with one family 800 series or 1000 series, one of the more simpler ones, and try to capture that series. If one series of parts is too bulky or complicated that is your answer, you may need to isolate each part by itself.
> 
> I would not try to cross vendors to the stm or lpc/nxp cortex-m3 or cortex-m0 parts etc.  the memory maps and peripherals across vendors are too different.  boot strategies, flash programming, etc.  


The great strength of ARM is that the peripherals, even if in different locations in different manufacturers parts, are identical in hardware terms if they are all cortex m3; that is the IP which they license from ARM.com. So maybe that is another reason for keeping the peripheral offset definitions and peripheral drivers separate and out of the compiler.

Geoffrey


> I suspect everyone using an arm7 in a controller now will be using one of the cortex-m cores before long if they are not already.
>  Is it st or lpc that has both cortex-m3 and cortex-m0 based parts now?  I would have to look up the difference but know I bought/saw both at some point.
> 
> David
> 
> 
> 
> On 08/20/2011 02:20 AM, John Clymer wrote:
>> Also, just peeked at current line up of STM32 controllers, there are 150
>> different controllers available, consisting of 33 possible combinations
>> of FLASH memory and SRAM size.
>> 
>> I will try to get the controller specific parts boiled up into record
>> structures this weekend, and get some added controllers installed into
>> cpuinfo.pas. (And fix any compiler breakages from the change.) I have
>> the SVN download - so generated diffs should be a bit easier (still
>> learning SVN though...)
>> 
>> Also, I read through the ARM docs regarding the "standard" library - and
>> can setup registers based on the each vendors published "C" library so
>> they match the ARM/vendor docs. However, as each controller in the
>> line-up has only certain peripherals, is it the intention that EACH
>> controller gets it's own controller file with memory definitions for
>> peripherals ? That's 300+ unit files between STM32 and TI's Stellaris
>> line-ups.
>> 
>> OR - does one try to merge as many controllers into 1 memory definition
>> as possible. i.e. ALL of stellaris could be defined for the maximal
>> configuration of peripherals (as they have a standard mapping layout for
>> peripherals i.e. ALL LM3 devices have UART0 at the exact same location -
>> and all have the same register layout.) The caveat to this that one
>> could compile code that won't actually run on a given device.
>> 
>> OR - we could leave the peripheral definitions to the user. (Which I'm
>> assuming is not the preferred route.)
>> 
>> John
>> 
>> ------------------------------------------------------------------------
>> *From:* Florian Klämpfl <florian at freepascal.org>
>> *To:* FPC developers' list <fpc-devel at lists.freepascal.org>
>> *Sent:* Fri, August 19, 2011 12:19:05 PM
>> *Subject:* Re: [fpc-devel] Arm Thumb2 - Stellaris status
>> 
>> Am 19.08.2011 05:28, schrieb John Clymer:
>> > Currently, everything is in a handful of giant arrays. Just wondering
>> > if it would be better to switch to a record structure for the controller
>> > entries - rather than individual arrays. (Add in a variety of STM parts
>> > and the other manufacturers, and there could easily be over 100 memory
>> > configurations in the table.)
>> 
>> Maybe it's indeed better to have an array of records, each record
>> describing one controller.
>> 
>> >
>> > My suggestion would be that the register definitions come in an UNIT
>> > file that only defines registers. The controller unit in the compiler
>> > source would only provide the bare minimum necessary to bring the system
>> > up and call PASCALMAIN. However, if it is deemed better to have the
>> > entire register set defined inside the RTL - that would be fine too.
>> 
>> Well, isn't it for a user easier just to pass the controller he uses on
>> the command line and the compiler does the rest? Why bother with
>> addional uses etc. if the compiler knows already anything?
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