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Used interrupts on both 68k & PIC, want 68k w/onboard memory & JTAG/BDM

Discussion in 'Embedded' started by 2Penny, Sep 5, 2008.

  1. 2Penny

    2Penny Guest

    Gentlemen -

    The subject line says it all. I've just started looking
    around for a 68k-ish creature with some PIC-like features
    that might have popped up recently. Has anyone here seen
    this beast? Where?

    2Penny (my 2 cents worth)
    2Penny, Sep 5, 2008
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  2. 2Penny

    Didi Guest

    Well not sure what PIC-like features means, but if you are after
    a tiny MCU with a reasonably powerful 68k (50 MHz), have a
    look at the coldfire line, the MCF51QE (IIRC the name) is
    available and there are another few similar ones promised.

    Didi, Sep 5, 2008
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  3. 2Penny

    larwe Guest

    It's called ColdFire now. Look at Freescale's website for all the data
    you could hope to get - there are plenty of CF parts with on-chip
    flash and RAM and all of them have embedded debug (JTAG).

    I can give you gratis an EVB with a ColdFire micro on it, asking only
    that you pay shipping. The particular part in question (MCF51JM128)
    has I think 128K flash, 16K RAM and on-chip USB.

    However, if the answer is 68k then the question may have been asked
    wrong; 68K/CF is more or less an obsolescent architecture these days.
    The impression I have from Freescale's literature is that CF exists
    only to provide a somewhat source-leve upward migration path from
    68HC09 8-bit apps, without the cost [to Freescale] of an ARM license.
    larwe, Sep 5, 2008
  4. 2Penny

    Didi Guest

    Hey, that 09 (apparently you meant 08) typo can bring memories
    to some here (like myself, having grown up on a 6809 CPU, which
    has been dead for 20 years now).

    The CF line - especially the tiny ones you refer to - is good enough
    on its own, I don't see it having anything to do with ARM. And the
    parts - debug interface included - are 100% documented (don't know
    how this is for ARM). Unlike ARM, programming CF in 68k assembly
    is quite practical - which is a huge difference (for those who
    can take advantage of it, admittedly not many).

    Didi, Sep 5, 2008
  5. 2Penny

    2Penny Guest

    Ladies,Gentlemen -

    I knew something about Coldfire, but didn't know it had
    JTAG interface. Yes, I've done ASM programming and fully
    intend to use it again.

    Now about assemblers ...

    OK, the part lines up nicely enough, but where's the
    assembler from and at what cost?


    2Penny, Sep 5, 2008
  6. 2Penny

    Didi Guest

    Ouch, I think they have no JTAG - just a so called "1 wire debug
    interface" or something. It is documented but I have not dealt
    with it yet, including these parts in my toolchain is only on
    my TBD list...
    This pretty much means no boundary scan, I believe (again, not
    sure what can be done over the debug interface).
    I can't help here since I use my own, DPS based toolchain
    which is not available for any popular hardware platform.
    Since you know 68k ASM I suppose you will either know you
    have to stay away from the weird GNU 68k syntax or be used
    to it and just use it... :).


    Dimiter Popoff Transgalactic Instruments


    Original message: http://groups.google.com/group/comp.arch.embedded/msg/75d8be2275ea72aa?dmode=source

    Didi, Sep 5, 2008
  7. 2Penny

    David Brown Guest

    You don't need to address the group so formally - but you *do* need to
    learn to post correctly (quote properly without extra indents, and don't
    The Coldfires do not have a JTAG interface (some do, but it's not for
    debugging). They have a BDM interface which is a Freescale-specific
    serial debugging interface. It does a similar job to JTAG debugger
    interfaces, but is more efficient.
    Get the gcc toolchain from www.codesourcery.com. This includes the gnu
    assembler and linker, gcc C and C++ compilers, a library, and other
    tools. You can get the completely free version (free as in beer and
    free as in speech), or pay for a supported version with integrated
    Eclipse and some extra utilities.

    An alternative would be Code Warrior from Freescale, which is free for a
    limited code size.
    David Brown, Sep 5, 2008
  8. 2Penny

    David Brown Guest

    That may be the impression *you* have got of the ColdFire, but it is
    totally at odds with reality. The ColdFire is very much a major 32-bit
    processor architecture with devices ranging from tiny low-power with
    integrated memories to superscaler devices at several hundred MHz.
    Freescale have a couple of dozen devices available, with new ones coming
    out all the time. The cores are also available for license - I read
    somewhere (but haven't confirmed) that there are more ColdFire cores in
    ASICs than in all of Freescale's MCF device range put together.

    The ColdFire core bears no resemblance to the 8-bit Freescale cores -
    perhaps you are thinking only of the ColdFire v1 cores that are
    available in the same package and with the same peripherals as a range
    of 68S08 devices (the idea being that you can easily move between
    cheaper and lower power 8-bit cores and faster 32-bit cores).

    I don't know that many people would describe the ColdFire as "PIC-like",
    however. When you mention "PIC", experienced embedded developers tend
    to think of nice peripherals and a horrendously ugly core, while people
    who know the ColdFire core think of it as one of the most elegant
    designs available (and with good peripherals too).
    David Brown, Sep 5, 2008
  9. 2Penny

    larwe Guest

    Mere availability of a wide range of devices is an orthogonal issue to
    the matter of obsolescence. ColdFire is used, yes, but (if you buy the
    reports) it's experiencing a shrinking number of design wins.
    Freescale as a whole isn't doing amazingly well these days, FTM.
    .... exactly like the popular cores, viz. ARM and MIPS. ColdFire
    occupies the same space for Freescale that AVR32 does for Atmel (and
    most of the other silicon vendors have their own proprietary 32-bit
    cores, too - NEC, ST, ...). They're generally available but not really
    what one would call mainstream.
    Yes, that's what I meant. Wasn't implying any architectural similarity
    between the cores, I was talking about the migration path Freescale
    larwe, Sep 5, 2008
  10. 2Penny

    Didi Guest

    Coldfire appeared after Motorola had closed the 68k line at 68060;
    to me it looks like extending the life of the 68k architecure which
    was so much ahead of its time that it is still hard to scrap.
    They wanted to replace it with the PPC - which is still by far the
    most advanced architecture on the market today - but 15+ years on
    this has yet to be 100% completed...
    Much of the reason - perhaps not quite recognized - is the fact that
    68k assembly is an extremely efficient language. Extending that
    into VPA has made me even more efficient on PPC platforms, however
    this is not (perhaps yet) available for a wider audience.
    And using a 68k using C is more or less pointless, there is no
    advantage to have with that - just use PPC or ARM or whatever.
    The tiny coldfires compete for the lowest power market segment, only
    the 430 is in that category. And CF has that true 68K style IRQ
    priority scheme, none of the rest have it (and very few poeople
    know what to do with it, of course).

    Didi, Sep 5, 2008
  11. 2Penny

    ChrisQ Guest

    Have been a long term fan of 68k and considering that it's been around
    since 1979'ish, has to be one of the longest lasting embedded 16 bit
    architectures around. A clean, orthoganal design with (as you say) a
    fully vectored prioritised interrupt subsystem that's hard to better 25+
    years later. Renesas copied it almost verbatim in the M30870.. series
    and probably many others as well.

    Looked at coldfire and wanted an excuse to use it, but can't ignore the
    logic of arm, which has dozens of vendors. Parts are cheap and powerfull
    as well and you just have to live with stuff like the idiosyncratic
    interrupt structure. Nothing like as clean as 68k, but I guess that's
    progress and still haven't really forgiven Freescale for eol'ing
    Dragonball 68k at pretty short notice...

    ChrisQ, Sep 5, 2008
  12. 2Penny

    linnix Guest

    One good thing about Coldfire is that the V1 IP is relatively cheap.
    I think it's 10K plus 1 penny each. So, if you are into ASIC, you can
    keep it alive for ever.
    linnix, Sep 5, 2008
  13. 2Penny

    Didi Guest

    The "dozens of vendors" thing is largely overestimated in its
    importance, not one ARM based part is really second sourced. The
    common thing they have is the core which also varies widely,
    like many others. Then the tiny CF (pretty new, some of them
    still just "sample") addresses the lowest power market (while
    you still have a 50 MHz 68k...), I don't know if ARMs do that.

    Other than that, I also have looked at the CF line and rejected
    it about 8 or 9 years ago. It was just emerging, and I had to move
    on from the CPU32 (I used the 68340, still available, unlike your
    Dragonball...); my judgment was that my (huge amount of) code,
    written in CPU32 ASM would be better off using just source level
    compatibility rather than binary, the CF would have been a lot
    worse off emulating all the addressing modes it did not have than
    the PPC doing it at the expense of somewhat longer binaries (which
    turned out to become apr. 3.5 times larger than the original CPU32
    ones, no optimization whatsoever - with much room for some).
    But the tiny CF parts - which are all <$5, some are closer
    to $2 - are really interesting and have what it takes to
    become popular, I believe.

    Didi, Sep 6, 2008
  14. 2Penny

    larwe Guest

    How can they compare to a sub-$1 Cortex-M3 part with 64K flash, 16K
    RAM, and loads of peripherals?
    larwe, Sep 6, 2008
  15. 2Penny

    Didi Guest

    Perhaps someone familiar with both families could comment,
    I am not that familiar with ARM and you don't seem to be
    very familiar with CF. Actually I have yet to become very
    familiar with it myself, but I have already done some work
    in this direction.
    How much does the part you refer to consume running full power
    at 50 MHz core clock? The MCF51QE128 @3.3V, 50 MHz core/25 MHz bus
    specifies 33.4 mA - everything on and running, obviously it
    goes down through uA to nA range using different power saving
    The prices I know of are for 1000+, are yours at 1000+ as well?

    Didi, Sep 6, 2008
  16. 2Penny

    larwe Guest

    My point is that there needs to be a compelling reason to choose a
    proprietary core. I remember having the same argument in this NG about
    AVR32. The Atmel guys have given up on trying to sell it to us, when
    they come round to talk about products they just say "oh, and of
    course there's AVR32 as well". Microchip keeps trying to sell us the
    32-bit PICs... which reminds me they were going to give me an EVB to
    play with at home. I must ping them about that.
    The part isn't characterized at that precise frequency (it is
    characterized from 8 to 72MHz in various steps), but at 48MHz core,
    fbus=fcore (but 1WS, effectively 24MHz) it's 36.1mA with all
    peripherals enabled, 24.4 with all peripherals disabled (running from
    flash) or 31.5/20.5mA running from RAM. Definitely the same ballpark.

    That's why I got puzzled when you or someone else in this thread
    started talking about low power consumption; CF simply isn't amazingly
    slender in this day and age. Low-power apps that don't require much
    horsepower go with an 8-bitter or an MSP430; apps that do require
    number-crunching horsepower often use a low-power DSP these days.
    We don't bother to get pricing for anything in quantities under
    10000 :)
    larwe, Sep 6, 2008
  17. 2Penny

    Didi Guest

    I do not see how ARM is more mainstream than 68k, other than
    in marketeer talk. What do you get if your MCU is ARM based
    and not CF or whatever? It is still single sourced. There is
    likely more 68k code around than there is ARM - has been used
    much longer in much larger applications than ARM goes into.
    There must be some compelling reason nowadays with all that
    C programming mess to prefer a part based on its core anyway;
    access to an efficient assembly language for someone who can
    take advantage of it looks like one to me.
    Same ballpark indeed, if the ARM based part has also the lowest power
    saving modes - slower internal clock etc. - this becomes even more so.
    So prices are the same. Well, I am sure I could pack a lot more code
    into a CF part than anyone could pack using C in either ARM or CF
    (factor of 10+) and I would be faster practically for any project
    larger than something saying "hello world", so I know what my choice
    would be.

    Didi, Sep 6, 2008
  18. 2Penny

    linnix Guest

    In a way, we have to thank the x86 marketer for beating the 68k.
    Otherwise, many programmers would stay with assemblers and C would not
    be as popular. C masks out the ugly x86 architecture.
    linnix, Sep 7, 2008
  19. 2Penny

    Didi Guest

    Indeed so. The world has to thank x86 for making C popular and
    thus totally messing up programming for decades - so far.
    This probably sounds weird to almost everyone; likely because
    C has always been the only thing "everyone" has ever been good

    Didi, Sep 7, 2008
  20. The strange thing is that C became so common and not PLM-86.

    A few years earlier, most 8-bitters were programmed in assembler, but
    Intel marketed the PLM-80 to mask the ugly 8080 architecture. PLM-80
    was used quite a lot in those days.

    Paul Keinanen, Sep 7, 2008
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