Michael Chapman wrote:
> tns1 wrote:
>> Paul Keinanen wrote:
>>> On Wed, 13 Aug 2008 11:44:43 -0700, tns1 <tns1@cox.net> wrote:
>> ...
>>> If you already require a 32 bit integer processor, are you sure you
>>> need HW floating point ?
>>>
>>> With 32 bit integer hardware single precision multiplication/division
>>> is quite trivial (unless you need full IEEE compliance :-).
>>>
>> The existing system uses a HW FPU, so its just easier to require this 
>> on the new system rather than do the up-front analysis to justify 
>> using a SW solution. As long as it could do basic single precision 
>> operations and was IEEE754 compliant I suspect it would be OK. Like so 
>> many projects I need to architect a general solution before all the 
>> details are known.
> 
> Any decent 'C' compiler on an embedded processor gives a good emulation 
> of single and double precision floating points operations. Most of these 
> are IEEE754 compliant (as opposed to many HW implementations which are 
> not).
> 

Most decent compilers (and libraries) will give you a choice of 
compliant behaviour or non-compliant but smaller and faster behaviour. 
They also (except perhaps for small cpus which are wholly unsuited for 
complex maths) normally implement both singles and doubles, and 
sometimes long doubles - hardware implementations are often limited to 
single precision.

> The only advantage of a HW implementation is speed. If the SW one is 
> fast enough on the processor you have selected then there is no need 
> whatsoever for the HW.
> 

I think hardware floating point can make sense on specialised devices, 
such as floating point DSPs.  But for general usage, there are few 
advantages and many disadvantages until you are talking about much 
larger cpu devices such as x86 or PPC architectures.

tns1 wrote:
> Paul Keinanen wrote:
>> On Wed, 13 Aug 2008 11:44:43 -0700, tns1 <tns1@cox.net> wrote:
> ...
>> If you already require a 32 bit integer processor, are you sure you
>> need HW floating point ?
>>
>> With 32 bit integer hardware single precision multiplication/division
>> is quite trivial (unless you need full IEEE compliance :-).
>>
> The existing system uses a HW FPU, so its just easier to require this on 
> the new system rather than do the up-front analysis to justify using a 
> SW solution. As long as it could do basic single precision operations 
> and was IEEE754 compliant I suspect it would be OK. Like so many 
> projects I need to architect a general solution before all the details 
> are known.

Any decent 'C' compiler on an embedded processor gives a good emulation 
of single and double precision floating points operations. Most of these 
are IEEE754 compliant (as opposed to many HW implementations which are not).

The only advantage of a HW implementation is speed. If the SW one is 
fast enough on the processor you have selected then there is no need 
whatsoever for the HW.

tns1 wrote:
> Paul Keinanen wrote:
>> On Wed, 13 Aug 2008 11:44:43 -0700, tns1 <tns1@cox.net> wrote:
> ...
>> If you already require a 32 bit integer processor, are you sure you
>> need HW floating point ?
>>
>> With 32 bit integer hardware single precision multiplication/division
>> is quite trivial (unless you need full IEEE compliance :-).
>>
> The existing system uses a HW FPU, so its just easier to require this on 
> the new system rather than do the up-front analysis to justify using a 
> SW solution. As long as it could do basic single precision operations 
> and was IEEE754 compliant I suspect it would be OK. Like so many 
> projects I need to architect a general solution before all the details 
> are known.

Do you *really* need IEEE754 compliance, or is that just a buzzword 
someone has put in without clarification?  At its simplest, IEEE754 
means using the standard format for single and double float formats, and 
specifies a required level of accuracy for arithmetic operations.  But 
full compliance requires handling of NaNs, denormalized numbers, 
rounding modes, signed zeros, and other such features that are very 
seldom needed - and almost never in embedded systems.  Many HW FPU units 
can't provide full compliance (and they are often limited to single 
precision), and need software traps and other mechanisms that end up 
slower than a software-only solution if you really need these features.

Paul Keinanen wrote:
> On Wed, 13 Aug 2008 11:44:43 -0700, tns1 <tns1@cox.net> wrote:
...
> If you already require a 32 bit integer processor, are you sure you
> need HW floating point ?
> 
> With 32 bit integer hardware single precision multiplication/division
> is quite trivial (unless you need full IEEE compliance :-).
> 
The existing system uses a HW FPU, so its just easier to require this on 
the new system rather than do the up-front analysis to justify using a 
SW solution. As long as it could do basic single precision operations 
and was IEEE754 compliant I suspect it would be OK. Like so many 
projects I need to architect a general solution before all the details 
are known.

On Wed, 13 Aug 2008 11:44:43 -0700, tns1 <tns1@cox.net> wrote:

>
>40-60MIPS performance, 32bit single core
>HW floating point

If you already require a 32 bit integer processor, are you sure you
need HW floating point ?

With 32 bit integer hardware single precision multiplication/division
is quite trivial (unless you need full IEEE compliance :-).

Float add/sub are a bit more costly due to the normalization and
demoralization required, but if the HW supports multiple bit shifts,
in which the shift count can be variable (e.g. specified in a
register), the 32 bit integer processor can handle floating points
quite effectively.

On the other hand, I would very much prefer a float/double FPU, if the
main CPU is only 8/16 bits.

Paul

tns1 wrote:
> I have been looking at current mainstream 32bit embedded processors for 
> my project (ARM, cortex, PPC, coldfire, etc). I would sure like to find 
> a single device that has most of what I need, but I am running out of 
> places to look. The main problem is memory support.
> 
> The wish list is:
> cortex M3
> 40-60MIPS performance
> simple
> 3 banks of Flash 1MB internal, 512KB, 256KB
> 2 banks of RAM 1MB, 512KB
> 4+uarts
> wdt
> rtc
> lcd support
> A/D
> D/A
> 
> I don't expect to find one device that has all that built in, but I'd 
> expect when you start with a core that has 4GB address space there would 
> be at least a few devices supporting a good chunk of that. Instead there 
> are lots of devices with no more than 512K internal code Flash, and 64K 
> internal SRAM. If they have more it is broken up into small 
> non-contiguous pieces. An example is the STR912. Most of the bells and 
> whistles I want, high speed internal flash and sram, but just not enough 
> of it.
> 
> External memory support is either limited, not mapped contiguous with 
> internal memory, or some hokey bank switched scheme. Give me a few more 
> address lines or programmable ext. chip selects.
> 
> At the other extreme are devices with much higher clock speeds, almost 
> no internal memory but huge external memory support. These are typically 
> large BGA packages and one look at the data sheet tells you that the 
> design is going to take a lot longer and have an extra 2-4 layers.
> 
> Isn't there anything between these extremes?
> 
> 
> 
After more study, the requirements are a bit different. The addition of 
an FPU and MMU eliminated many of my prior choices. Instead of focusing 
on the processor, it is probably more important to look for an existing 
dev board with most of these features and good tools support, since a 
custom board could delay SW development.

40-60MIPS performance, 32bit single core
HW floating point
MMU is optional but preferred
Support for at least two separate banks of sectored NOR style Flash 
internal or external. Bank1 is 1MBmin execute-in-place, bank2 is 
512KBmin. A single large bank could work.
Support for at least two separate banks of RAM internal or external. 
Bank1 is 1MB min, bank2 is 512KB min, battery backed SRAM.
1 ethernet
qvga lcd support
4+uarts
wdt,rtc,A/D,D/A

I realize that some of the items like the D/A and extra memory banks or 
uarts will not be found on a dev board. That's fine as long as the 
processor will support adding these to the project board. I do need at 
least one big chunk of NOR Flash, and RAM each.

The best fit so far is the Phytec LPC3000 boards.
The Logic Card Engine boards look promising too.

As interesting as their chips are, I don't see any Infineon boards 
beyond the 'bare-bones' kits, and working their chips into the design 
would mean a larger BOM.

On 8 Aug, 00:46, tns1 <t...@cox.net> wrote:
> I have been looking at current mainstream 32bit embedded processors for
> my project (ARM, cortex, PPC, coldfire, etc). I would sure like to find
> a single device that has most of what I need, but I am running out of
> places to look. The main problem is memory support.
>
> The wish list is:
> cortex M3
> 40-60MIPS performance
> simple
> 3 banks of Flash 1MB internal, 512KB, 256KB
> 2 banks of RAM 1MB, 512KB
> 4+uarts
> wdt
> rtc
> lcd support
> A/D
> D/A
>
> I don't expect to find one device that has all that built in, but I'd
> expect when you start with a core that has 4GB address space there would
> be at least a few devices supporting a good chunk of that. Instead there
> are lots of devices with no more than 512K internal code Flash, and 64K
> internal SRAM. If they have more it is broken up into small
> non-contiguous pieces. An example is the STR912. Most of the bells and
> whistles I want, high speed internal flash and sram, but just not enough
> of it.
>
> External memory support is either limited, not mapped contiguous with
> internal memory, or some hokey bank switched scheme. Give me a few more
> address lines or programmable ext. chip selects.
>
> At the other extreme are devices with much higher clock speeds, almost
> no internal memory but huge external memory support. These are typically
> large BGA packages and one look at the data sheet tells you that the
> design is going to take a lot longer and have an extra 2-4 layers.
>
> Isn't there anything between these extremes?

A one-chip solution, off the shelf, with the amount of flash and ram
you are asking for is unlikely to exist, as other posters have pointed
out.

If a simple board design is more important to you than price: have you
considered buying a module, with chip + memory mounted on a small PCB?
Googling for "arm module" will give you a few hits.

tns1 wrote:
> I have been looking at current mainstream 32bit embedded processors for 
> my project (ARM, cortex, PPC, coldfire, etc). I would sure like to find 
> a single device that has most of what I need, but I am running out of 
> places to look. The main problem is memory support.
> 
> The wish list is:
> cortex M3
> 40-60MIPS performance
> simple
> 3 banks of Flash 1MB internal, 512KB, 256KB
> 2 banks of RAM 1MB, 512KB
> 4+uarts
> wdt
> rtc
> lcd support
> A/D
> D/A
> 
> I don't expect to find one device that has all that built in, but I'd 
> expect when you start with a core that has 4GB address space there would 
> be at least a few devices supporting a good chunk of that. Instead there 
> are lots of devices with no more than 512K internal code Flash, and 64K 
> internal SRAM. If they have more it is broken up into small 
> non-contiguous pieces. An example is the STR912. Most of the bells and 
> whistles I want, high speed internal flash and sram, but just not enough 
> of it.
> 
> External memory support is either limited, not mapped contiguous with 
> internal memory, or some hokey bank switched scheme. Give me a few more 
> address lines or programmable ext. chip selects.
> 
> At the other extreme are devices with much higher clock speeds, almost 
> no internal memory but huge external memory support. These are typically 
> large BGA packages and one look at the data sheet tells you that the 
> design is going to take a lot longer and have an extra 2-4 layers.
> 
> Isn't there anything between these extremes?
> 
> 

There is a conflict between the idle process parameters for making a RAM 
chip, a Flash device, and a microcontroller - they are all different 
(things like number and type of layers, size of features, type of 
doping, etc.).  Thus if you start with a microcontroller-optimised 
process, each bit of flash is significantly bigger, slower, and more 
expensive than if you start with a flash-optimised process.  So most 
microcontrollers have a relatively small flash (exceptions include some 
FreeScale MPC devices with up to 1 MB flash - costing something like $30 
more than the 0 MB flash version, and a few devices made with a 
flash-optimised process, which therefore have a bigger, slower, and more 
power-hungry microcontroller part).

This leads to two separate types of chips - microcontrollers, with up to 
something like 512K flash and 64K ram, and embedded microprocessors with 
no flash, and external databus, and typically a block or two of internal 
RAM (which is often good for the stack or other fast-access memory). 
There is not much in between.

If you have a full 32-bit databus, with something like 24 address pins 
and a bunch of control pins and chip selects, you quickly have 80 pins 
for the databus alone.  If the embedded microprocessor has a range of 
peripherals, especially things like lcd support or Ethernet, you get 
beyond the range of cheap non-bga packages very fast.

tns1 wrote:
> I have been looking at current mainstream 32bit embedded processors for 
> my project (ARM, cortex, PPC, coldfire, etc). I would sure like to find 
> a single device that has most of what I need, but I am running out of 
> places to look. The main problem is memory support.
> 
> The wish list is:
> cortex M3
> 40-60MIPS performance
> simple
> 3 banks of Flash 1MB internal, 512KB, 256KB
> 2 banks of RAM 1MB, 512KB
> 4+uarts
> wdt
> rtc
> lcd support
> A/D
> D/A
> 
> I don't expect to find one device that has all that built in, but I'd 
> expect when you start with a core that has 4GB address space there would 
> be at least a few devices supporting a good chunk of that.

Why ? that is rather strange reverse-logic.
Chips are built with memory that customer NEED, not with memory that the
bus might be able to address!. Price matters.

 > Instead there
> are lots of devices with no more than 512K internal code Flash, and 64K 
> internal SRAM. 

Because that is all they need, for most embedded applications.

<snip>
> At the other extreme are devices with much higher clock speeds, almost 
> no internal memory but huge external memory support. These are typically 
> large BGA packages and one look at the data sheet tells you that the 
> design is going to take a lot longer and have an extra 2-4 layers.
> 
> Isn't there anything between these extremes?

Not really, One is a Microcontroller, and one is a Microprecessor.
The Cortex M<3 targets bottom-end Microcontrollers in the 32bit space.

Your specs, especially the large RAM, push you into Microprocessor space.

The top end Automotive space tends to have the most flash, up to 4MBytes.

Perhaps Look at Infineons TriCore :
The TC116x has 1.5MByte in QFP, and you add the RAM ?

I think Freescale have some large-flash 1.5MBytes? PowerPC
variants, also in QFP.

-jg