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 Posted: Jan 15, 2012 - 09:46 AM |
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Joined: Feb 09, 2011
Posts: 335
Location: Turnhout, Belgium
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This is funny question IMHO. Of course the 8-bit MCU market is not destroyed and certainly not by ARM.
Why? The answer is simple: why should I use a 32 bit micro controller with way to much RAM/ROM when I don't need it?
In our applications we run a 8-bit MCU at 1.8MHz. The MCU market is way bigger than all the 'heavy' application which need high speed MCU's. People tend to forget that there is a world outside their own designs... |
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Posted: Jan 15, 2012 - 09:50 AM |
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Joined: Feb 09, 2011
Posts: 335
Location: Turnhout, Belgium
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Now for Atmel, Microchip or any other controller: main concern for us is: will the MCU we use still be available in 10 years and more?
There is no best, they are all evil buggers protecting their own product by making porting as difficult as possible. |
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Posted: Jan 15, 2012 - 10:58 AM |
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Joined: Feb 12, 2005
Posts: 16547
Location: Wormshill, England
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Kartman wrote:
I don't know why you guys are dumping on Leon in this instance. He stated a fact that no one has disproved - brand X sells more chips. We all know ( or should know by now), that Leon is not wedded to any one brand. Seems what is practised here is "brand racism". It probably doesn't happen in other similar forums as people there don't give crap.here there a very few unanswered posts, compare this with some other forums.
I agree 100%. The mantra may get a little boring, but Leon is honest.
Perhaps if he offered constructive advice when appropriate, people would be less offended.
As a general rule, you can do most things most of the time with an 8051, AVR, PIC, ARM or whatever. Sometimes one family is easier / faster / better / cheaper than another.
It seems quite reasonable to point out these occasions. All the same, design choices are made on several criteria. So you choose one family even though it is not ideal for one particular task.
David. |
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Posted: Jan 15, 2012 - 01:41 PM |
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Joined: Jul 18, 2005
Posts: 62944
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
Why? The answer is simple: why should I use a 32 bit micro controller with way to much RAM/ROM when I don't need it?
Only if a chip offering all the facilities you need in your design happens to be cheaper than the 8bit you were previously considering. Sure it may have 8 times as much flash and 4 times as much SRAM but if it's cheaper who cares? That (IMAO) is the real threat to 8 bit - when chips with the same spec or higher start to cost less why wouldn't you switch?
The arguments used to be (a) ah, but 8 bit are in DIP and I need that for small production runs and (b) ARM limits me to 3.3V design. Well apart from the fact that there are now (a) some ARM in DIP and (b) some 5V ARM, the fact is that most small (100 to 1000 units) producers can (a) now cope with SMD and (b) can find most solutions for the design in 3V3 anyway - in fact things like SD/MMC push them in that direction.
PS let's not make this thread about Leon and Microchip - he's ruined enough threads previously - don't let this be just another casualty - keep it on on-topic about ARM v 8bit
(Atmel probably wouldn't want us discussing even that here on their 8bit message board if it were not for the fact that they make quite a range of ARM and now Coretex themselves so you can stay loyal to Atmel). |
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Posted: Jan 15, 2012 - 01:58 PM |
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Joined: Jul 27, 2001
Posts: 7429
Location: St. Leonards-on-Sea (UK)
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| Power consumption is an important consideration these days, which no one has mentioned. I can't see any 32-bit device approaching the power consumption of many of the current low-power 8-bit chips, they simply have too many transistors. |
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Leon Heller
G1HSM
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Posted: Jan 15, 2012 - 02:06 PM |
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Joined: Jul 18, 2005
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Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
they simply have too many transistors
Does an M0 really have more transistors than, say, an Xmega?
(the core price of chips is set by their silicon area, which is set by the number of transistors. The fact that some M0 cost less than 8bit seems to suggest they may actually have fewer transistors in fact). |
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Posted: Jan 15, 2012 - 02:13 PM |
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Joined: Jul 27, 2001
Posts: 7429
Location: St. Leonards-on-Sea (UK)
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| I was thinking of smaller devices than the Xmega, which typically consume 20 nA or less in deep sleep mode. The low cost of some 32-bit parts is probably more to do with the manufacturing process than the number of transistors - they get a lot more die out of a wafer than is possible with the less advanced processes used for most 8-bit devices. |
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Leon Heller
G1HSM
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Posted: Jan 15, 2012 - 02:36 PM |
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Joined: Feb 19, 2001
Posts: 26114
Location: Wisconsin USA
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Quote:
Does an M0 really have more transistors than, say, an Xmega?
(the core price of chips is set by their silicon area, which is set by the number of transistors. The fact that some M0 cost less than 8bit seems to suggest they may actually have fewer transistors in fact).
Hmmm--There is still "what the market will bear" factor.
Does a Mega329 have less transistors than a Mega169? No? Then why did, for several years, the '169 price be higher than the '329 price?
A certain model could even be a loss leader--lose only a penny each but make up for it in volume. 
In general I'd assume that the cost to produce corresponds to the selling price.
[In the 1970s a model of mainframe computer had twice the clock speed/performance of the next lower model. And cost many $10000 more. One changed from the slower model to the faster model by snipping a clock-divider jumper on the backplane.] |
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Posted: Jan 15, 2012 - 05:32 PM |
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Joined: Sep 12, 2009
Posts: 2474
Location: Sacramento, CA
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jan_dc wrote:
This is funny question IMHO. Of course the 8-bit MCU market is not destroyed and certainly not by ARM.
Why? The answer is simple: why should I use a 32 bit micro controller with way to much RAM/ROM when I don't need it?
But what if all that unnecessary RAM/ROM came on a chip that still cost less? Surely you wouldn't buy the more expensive chip just because it was 8 bits, or had less RAM/ROM, any more than you'd buy a 6.3v 0603 cap that cost more than a 10v 0603 cap, because you didn't need a 10v cap.
Quote:
In our applications we run a 8-bit MCU at 1.8MHz. The MCU market is way bigger than all the 'heavy' application which need high speed MCU's. People tend to forget that there is a world outside their own designs...
There's no penalty in running a fast micro slowly. |
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Posted: Jan 15, 2012 - 05:44 PM |
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Joined: Oct 05, 2006
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Location: Poland
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leon_heller wrote:
I can't see any 32-bit device approaching the power consumption of many of the current low-power 8-bit chips, they simply have too many transistors.(...)I was thinking of smaller devices than the Xmega, which typically consume 20 nA or less in deep sleep mode.
This is not a power consumption but a power-down current.
Don't you think it does not matter what the power-down mode current is, as far as it is within the order of magnitude of self-discharge rate (shelf-life) of the cell/lemon that powers it?
Lets face it: the smallest commercial batteries are about 40mAh, which, with 20nA discharge rate give:
40e-3Ah/20e-9A=2e6h (of sleeping time).
Do you know how long it is? I don't, but it falls somewhere in XXIV-th century.
Why does it matter if the chip has below 20nA deep sleep current, or below 200nA, like CM0? Or below 100nA like P-AVRs? What is the advantage?
Perhaps if there were 0805-like cheap-as-dirt 5mAh cells that have the shelf-life of 50 years.. But I have never heard about those.
@leon_heller
Could you give an example of the (hypothetical) application where such insanely low power-down current would be of any practical value other than a marketing slogan for the manufacturer? |
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Posted: Jan 15, 2012 - 06:12 PM |
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Joined: Jul 27, 2001
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Location: St. Leonards-on-Sea (UK)
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Consumptions in other modes are typically very low, also.
Such devices are claimed to be useful for applications where a single cell has to last for up to 20 years. Power by energy harvesting is another area.
I can't see 32-bit devices being suitable for such applications. |
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Leon Heller
G1HSM
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Posted: Jan 15, 2012 - 07:09 PM |
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Joined: Jul 18, 2005
Posts: 62944
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
Hmmm--There is still "what the market will bear" factor.
Does a Mega329 have less transistors than a Mega169? No? Then why did, for several years, the '169 price be higher than the '329 price?
Lee, I take your point but I was talking more "industrial pricing" where market economics don't usually play too much part and silicon tends to sell at "cost + 10..30% profit for silicon vendor". In that realm silicon area is key.
BTW Leon is wrong - Atmel closed their fabs and contracted out to modern fab plants so the whole point of all the "A" devices is surely that they are now being made on a fairly contemporary process (0.12um? maybe smaller still?) which is probably very similar to M0/M3 in fact.
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I can't see 32-bit devices being suitable for such applications.
Someone tell my mobile phone! |
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Posted: Jan 15, 2012 - 07:16 PM |
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Joined: Jul 27, 2001
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Location: St. Leonards-on-Sea (UK)
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| I was thinking of applications which don't need a lot of processing power that might have to run for months or years on a single cell. |
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Leon Heller
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Last edited by leon_heller on Jan 15, 2012 - 07:18 PM; edited 1 time in total
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Posted: Jan 15, 2012 - 07:17 PM |
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Joined: Nov 17, 2004
Posts: 6144
Location: Great Smokey Mountains.
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| My crystal ball says that someday they'll put an ARM with all the desirable peripherals and pre-programmed with Arduino-simple methods to use them, all on a sub $1.00 chip. And since the silicon will be so tiny that it will be a sub 1 volt device that uses almost no power, so they will build in a battery that lasts 20 years. The PC will be so powerful that you'll just tell it what you want you micro to do and it will write the program for you. And my wife will leave me because I'm spending too much time with my sex-bot. |
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Posted: Jan 15, 2012 - 07:19 PM |
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Joined: Jul 27, 2001
Posts: 7429
Location: St. Leonards-on-Sea (UK)
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| That might happen, but 8-bit devices will be needed for a good few years yet. |
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Leon Heller
G1HSM
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Posted: Jan 15, 2012 - 07:36 PM |
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Joined: Jan 23, 2004
Posts: 9887
Location: Trondheim, Norway
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Quote:
I was thinking of applications which don't need a lot of processing power that might have to run for months or years on a single cell.
Past a certain point, the biggest issue is self-discharge of the battery cell. For some appplications super-super-super low power is great, but in most cases the battery will deplete itself at a rate faster than the processor is consuming it anyway.
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My crystal ball says that someday they'll put an ARM with all the desirable peripherals and pre-programmed with Arduino-simple methods to use them
If I remember right Arduino is branching out into the ARM devices, so your future might come faster than you'd think. Who knows what we'll all be using in 10 years time, if the software tools catch up to the device complexity.
- Dean  |
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Posted: Jan 15, 2012 - 08:57 PM |
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Joined: Feb 09, 2011
Posts: 335
Location: Turnhout, Belgium
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kk6gm wrote:
jan_dc wrote:
This is funny question IMHO. Of course the 8-bit MCU market is not destroyed and certainly not by ARM.
Why? The answer is simple: why should I use a 32 bit micro controller with way to much RAM/ROM when I don't need it?
But what if all that unnecessary RAM/ROM came on a chip that still cost less? Surely you wouldn't buy the more expensive chip just because it was 8 bits, or had less RAM/ROM, any more than you'd buy a 6.3v 0603 cap that cost more than a 10v 0603 cap, because you didn't need a 10v cap.
Quote:
In our applications we run a 8-bit MCU at 1.8MHz. The MCU market is way bigger than all the 'heavy' application which need high speed MCU's. People tend to forget that there is a world outside their own designs...
There's no penalty in running a fast micro slowly.
ok, I was a bit unclear I'm afraid. I'm not talking about mega and xmega cores. I'm talking about tiny stuff. Of course if a 32 bit fits the job and is cheaper, I'll use that. Haven't found any 32 bit yet that is overall cheaper. |
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Posted: Jan 15, 2012 - 09:17 PM |
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Joined: Oct 05, 2006
Posts: 2297
Location: Poland
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Such devices are claimed to be useful for applications where a single cell has to last for up to 20 years.
Either it is some niche market of tailor-made devices you mention (medical? aerospace?) or there is a technology I am not aware of. AFAIK the longest shelf life of the batteries are the lithium type primary cells which are capable of 10 years shelf-life/operating life (and perhaps 15 years with some extra design and conditions).
Are there any 20 years*20nA= +- 3,5mAh cells on the market?
What I wanted to ask about was
Brutte asking Leon Heller wrote:
"How is an engineer like me able to exploit the 20nA feature using contemporary technology?"
because you didn't give the direct answer. I understand there are 20nA chips, but are there "20nA compliant batteries"? I am sure Brand X made a significant (and costly) effort to compete with Brand N to reduce the leakage of their design. If they did it - great, but how am I able to use their product? Some kind of reference design, success story?
A device designed to be capable of running 20 years is rather peculiar. If the device has to perform some useful computations, apart from being in deepest power-down, the 3,5mAh is playing less and less significant factor in the total energy consumed when the computations demand (taken as a variable in the design) rises. So I can imagine a hypothetical device which runs for 19,999 years pretending dead, just to blink a LED on it's twentieth birthday. Even then the feature is pointless because we are not able to buy the 3,5mAh battery.
I personally doubt that any of the commercial battery manufacturers can guarantee his product is able to withstand this time (self-discharge current manufacturing variations).
If we assume a more reasonable 10 years operating time, rising the active time requirement we come to a point where there are batteries of adequate size available, but then even a 10x1,7mAh=17mAh leakage current(200nA) is still insignificant.
My conclusion is that I do not really understand why did Brand N make an effort to design LPCs with 200nA power-down/leakage current. This feature is useless, because there are no adequate (small capacity) batteries available.
EDIT: Corrected 3,5mA to 3,5mAh |
Last edited by Brutte on Jan 16, 2012 - 01:04 PM; edited 2 times in total
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Posted: Jan 15, 2012 - 09:25 PM |
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Joined: Nov 02, 2009
Posts: 3239
Location: Zelenograd, Russia
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| LPC1111 is $2 retail, $0.88 in 1000s. |
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Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.
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Posted: Jan 15, 2012 - 09:28 PM |
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Joined: Jul 27, 2001
Posts: 7429
Location: St. Leonards-on-Sea (UK)
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| Lithium iodide batteries can last over 15 years, and new chemistries will probably become available. Then there is energy harvesting, for which very low power is desirable. |
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Leon Heller
G1HSM
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