Re: ARM7 with longevity of supply

"rickman" <gnuarm@xxxxxxxxx> wrote in message
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Tom Lucas wrote:
"PeteS" <peter.smith8380@xxxxxxxxxxxx> wrote in message
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Tom Lucas wrote:
I've narrowed down my choices using the following criteria:
* Must have full IAR compiler support including headers,
flashloaders
and examples.
* Must have an external bus to connect to 8bit peripherals and
also
RAM/ROM.
* Must have JTAG interface.
* Must have minimum 16bit timers, preferably 32 bit.
* Must have watchdog timer.
* Must not be in a BGA package.

I believe this narrows the selection down to the following parts:
Freescale MAC7111
Phillips LPC2292/2294
ST Electronics STR710/750 (non-BGA flavours)

Who am I to argue with your requirements, but you might reconsider the
need for an 8 bit bus. These days most I/O is done directly from the
MCU or if expansion is needed, using SPI or I2C. If you tell us what
you need on the other end of the 8 bit bus maybe we can help you see
how easy it is to use one of the serial interfaces.

This is an issue because adding a data and address bus to an MCU
greatly increases the pin count and package size and therefore cost.

You are right in what you say and realistically I could probably do away
with a lot of the latches and flip-flops that expect 8 bit busses
(probably into an FPGA). However, I am only intending to replace the
processor area of an existing and working design and don't want too much
upheaval. It's less than ideal I know but gettign management to move
away from 80188 will be hard enough without having to redo the rest of
the system.

Seems something in the TI TMS470 series might fit the bill, if
you're
still looking at stuff. I'm designing a new product around one of
these for various reasons, and TI has given me assurances they are
going to be produced for at least the next 6 years (that's as far
as
the roadmap goes, apparently).

Someone warned me off the TI parts because the data*** is
inaccurate
apparently and they won't talk to you unless you are tier 1
automaotive.
Something about high impedance not really being high impedance or
something. However, this is purely anecdotal and not something I have
personal experience of.

I think you will find that all MCUs these days have errata. I know
the
Atmel parts include it in the data *** so you can review them
yourself to see if they are a problem. I also don't think you will
find 5 years to be a problem for a product lifetime since nearly all
the ARM MCUs are relatively new and in high demand.

I think a lot of the longevity depends on large (probably automotive)
manufacturers adopting the microcontroller in question.

You can review some information on a large number of ARM MCUs at
www.gnuarm.com. Go to the resources page and scroll down to the ARM
chips section where you will find an ARM device comparison chart link.
I don't claim the information is complete or accurate, but it is a
good
start.

Very good link. Someone else posted it earlier but thanks anyway.

One observation, if you want lower power chips, Atmel and NXP
(Philips)
are about neck and neck with roughly half the power consumption of the
other vendors. These parts will actually run at lower power than many
8 bit cores when you run them at the same speed. This is due to the
smaller process geometries.

I have oodles of power available so that is one restriction I can be
free of.

Luminary Micro uses the Cortex-M3 core which is the latest from ARM
and
is specifically designed for embedded work. They wanted to get their
product out the door quickly, so they are using a 250 nm process and
their power is a bit higher than the others, but they have other parts
coming out in the spring. The Cortex-M3 core has some improvements in
code density, processing speed, exception handling and ARM has
standardized some of the peripherals which means you can port between
different chip makers more easily.

You might also ask about any of these chips in comp.sys.arm and in the
Yahoo groups for the different processor types, AT91SAM, LPC2000,
STR7,
ARMSTR, TMS470_ARM, ADuC_ARM, arm-user, ARM_Microcontroller,
OKI-ARM-mcus, arm32bit, stellaris_lm, Cortex-M3.



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