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Who has the lowest power MCU?

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xorbit
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re: Who has the lowest power MCU?
xorbit   4/12/2012 6:44:44 PM
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I don't know if this is still the case with newer parts, but it has been my experience in the past that Microchip parts looked good on paper, but sorely lacked when it came to actual real-world use. For instance, they would brag about ultra low power, but the only way to wake up the part would be to reset it. There were other things like that. Also, uA/MHz is an irrelevant number when comparing PICs with MSP430s. PIC is the Pentium 4 of microcontrollers: it gets very little done per clock cycle. So it needs to run at much higher MHz to get the same amount of processing done as the extremely efficient MSP430 architecture. A comparison in uA/DMIPS, taking the difference in DMIPS/MHz into account when running real code, would be much more useful for real-world comparisons. I can guarantee the picture would not look pretty for Microchip. Disclaimer: I do not work for either Microchip or TI, but I've compared the architectures in the past.

t.alex
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re: Who has the lowest power MCU?
t.alex   4/12/2012 10:50:12 PM
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Benchmarking like this is quite subjective and it is quite difficult to get a fair result. People typically look at the overall system/product rather than just the MCU.

Jason.Tollefson
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re: Who has the lowest power MCU?
Jason.Tollefson   4/12/2012 11:08:48 PM
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XORBIT, Thanks for your comments regarding Microchip’s PIC® MCUs, and you are correct that newer parts are much lower power than prior parts. For Sleep modes, Microchip offers up to three; Sleep, Low Voltage Sleep, and Deep Sleep. In every mode, PIC MCUs with eXtreme Low Power (XLP) Technology have multiple methods for waking from sleep, such as an RTC, a Watchdog Timer, Timers, and Interrupts. Regarding work done per clock cycle, I would ask you to examine the number of instruction cycles listed in the MSP430 User Guide, SLAU056G, Page 3-71. Depending on the type of memory addressed, the instruction can be up to 6 cycles for a single instruction. By contrast, 90% of PIC24F instructions are 1 cycle, which is 2 clocks. We tested this with the following C-code, which merely copies 32 bytes from one memory location to another: Sleep(); LATBbits.LATB2 = 1; memcpy(testArr1,testArr2,sizeof(testArr1)); LATBbits.LATB2 = 0; At 4 MHz, this resulted in an execution time of 32 µs for PIC24F, and 80 µs for MSP430. The resultant energy saved by the PIC24F over the MSP430 is 2X! We also ran side by side comparisons of PIC24F and MSP430 using industry-standard benchmarks and found that PIC24F executes code 1.5 to 5 times faster at a given frequency. I would ask you to take a second look at Microchip’s PIC MCUs with XLP Technology and reevaluate our performance in a real-world example. I think you may find that Microchip looks a lot better than you first thought. Disclaimer: I work for Microchip Technology Incorporated, which is committed to delivering outstanding value in low-power MCUs. -Jason Tollefson, 16-bit Microcontroller Senior Product Marketing Manager, Microchip Technology Inc.

KaiserSoze
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re: Who has the lowest power MCU?
KaiserSoze   4/13/2012 8:00:48 AM
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I note only this detail: to win over the MSP430, Microchip take the sleep/standby current of one item(PIC 24FJ12 etc, 16-bit), and the Active current of one other Item (PIC16LF etc, 8-bit). It seem to me a non-correct method of comparison. It would be the same if TI proposed the best data taking them from several devices, taking the best from where TI have convenience (but TI doesn't acts so). I think that these tricks aren't honourable for a big firm as Microchip. As PM EDT, I don't work for any of two rival.

xorbit
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re: Who has the lowest power MCU?
xorbit   4/13/2012 4:15:28 PM
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Jason, Indeed, as KaiserSoze brings out, it looks as if you're deliberately trying to mislead when you mix the best of each of your architectures as if there were one part that does it all, which isn't true. Unfortunately, I have gotten this feeling pretty much every time I have investigated Microchip parts when some impressive marketing claim had drawn my attention. Upon further investigation, there usually was some gotcha or clever specmanship involved, which has made me wary of any Microchip marketing claims. I couldn't find full specs on the MSP430 Wolverine parts, but just taking a quick look at your datasheet for the PIC24FJ128GA310 and the datasheet for the MSP430FR5720, I couldn't help but notice that Microchip's typical power consumption column on page 361 has a note saying "Data in the Typical column is at 3.3V, 25°C unless otherwise stated". But each row states -40°C to +85°C. Which is it? The MSP430 power specs seem to cover -40°C to +85°C. I'm not saying your claims are untrue, but previous experience has taught me to be very cautious of "the Microchip spin". I have also not evaluated the performance of the PIC24 series, I have previously compared the MSP430 to the PIC16 series, based on similar cost, and there was no contest there. I would suggest to anyone doing this evaluation to look carefully beyond the marketing and into the technical details. Also, there are other low power contenders around, the Renesas RL78 comes to mind (66uA/MHz).

Jason.Tollefson
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re: Who has the lowest power MCU?
Jason.Tollefson   4/13/2012 6:24:17 PM
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KaiserSoze and xorbit, Microchip submitted the above table to EE Times, to provide their readers with an at-a-glance comparison of published data. I agree with xorbit—don’t take either company’s word for it; investigate the source documents and decide for yourself which MCU will best meet your needs. Better yet, obtain samples and do your own comparison. -Jason Tollefson, 16-bit Microcontroller Senior Product Marketing Manager, Microchip Technology Inc.

t.alex
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re: Who has the lowest power MCU?
t.alex   4/13/2012 9:51:20 PM
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How about peripherals ?

KaiserSoze
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re: Who has the lowest power MCU?
KaiserSoze   4/14/2012 12:21:13 PM
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Hello Jason, Thanks for your answer. I agree with your thought "Try samples and examine results". And, overall, I'me sure that today TI and Microchip as well are making a good work and have interesting devices. On teh other hand,I don't agree with arbitrary misleading, as the one about the code to move data. Try to examine this one for MSP430, supposing two 32-bytes arrays starting at StrtAddr1 (source) and StrtAddr2 (dest): bis.b #TestBit,TestPort ;pin setted at the end of this move #16,r4 ;2T; 32 bytes are 16hword move #StrtAddr1,r5 ;2T loop: move @r5+,StrtAddr2-StrtAddr1-2(r5) ;5T dec r4 ;1T jnz loop ;2T bic.b #TestBit,TestPort ;4T Summing all states results in 8*16+8=136T (I apologize for mistakes); at 4MHz it means 32usec and not 80usec, please update your test results. Surely, "C" against "assembly" is a misleading comparison, I can't make the same error I find in someone's reasonement; But (I used PIC in early age, about in 1992, I dont' remember its assembly) try to write "16-byte-move" routine in assembly and compare results. That is, when between a uP task and uP code there is a Compiler, its behaviour can change things at all. In every case -and I conclude- I show I'm not blind: code compactness in MSP430 isn't good (eg: "byte" instruction are exactly long as "word" one; e.g: Hitachi H8s is better), and I remember PIC (I used old 16C71) was very very compact.On the other hand,Pic hasn't powerful instruction as "mov @r5+,OFFSET(r5) that atomically read WORD, write WORD and update pointer. Core comparison is often difficult, but You can't exaust this thema saying "PIC instruction are 1-cycle, TI are 1..6cycles, so we are SURELY better", without considering in detail the differences between the actions of one and other instruction. Have a good day

_hm
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re: Who has the lowest power MCU?
_hm   4/15/2012 1:28:36 PM
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Very interesting discussion. How about other vendors like Sillab and others?

Sanjib.A
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re: Who has the lowest power MCU?
Sanjib.A   4/15/2012 5:14:49 PM
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Any analysis done on the equivalent controllers from Free scale and others? By the way all the comments added to this discussion generates very useful information for the designers. Thanks for all the thoughts and experience shared!

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