Why are 8 bit micro's still around today? - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: March 30, 2016, 12:03:38 am
content: Why are 8 bit micro's still around today? and what are the main limitations that a 8 bit has against a 16 bit or 32 bit micro? apart from having "less bits " lol is there too much processing disadvantage ? talking about risc and arm and any architecture

author: ovnr
author_rank: Frequent Contributor
timestamp: March 30, 2016, 12:14:47 am
content: They're often slightly cheaper in volume? Industry inertia?Tbh, if the 8-bit micro series you've got tools for will do the job, there's little reason to change it.

author: Delta
author_rank: Super Contributor
timestamp: March 30, 2016, 12:23:55 am
content: Ultra low power.If you don't need a lot of processing grunt, why go for anything bigger?

author: station240
author_rank: Unknown
timestamp: March 30, 2016, 02:14:48 am
content: Quote from: little_carlos on March 30, 2016, 12:03:38 amLittle known fact, ARM is in fact the one surviving section of a company that originally made 8 bit computers.They experimented with other companies 32 bit processors, then gave up and made their own.Float point numbers are usually 32 bit, so using an 8 bit processor makes it take four times longer to process (or more).Also things like colour LCDs which use 24 bit colour. In cases like this, you actually gain speed simply by having a wider bus.

author: ade
author_rank: Unknown
timestamp: March 30, 2016, 03:05:18 am
content: Why 8-bit? Dave has it covered:https://youtu.be/1apCAzCTZdQ?t=36m48s(Link edited)

author: andyturk
author_rank: Frequent Contributor
timestamp: March 30, 2016, 03:23:50 am
content: Quote from: ade on March 30, 2016, 03:05:18 amI think Jack (the guy speaking) has it wrong though. The cost of licensing the Cortex M0 is only $40k USD (evidence). So while there is a little "ARM tax" involved in making an M0 chip, it's not much in the grand scheme of things. And it's probably much less than the programmer salary to maintain a compiler/IDE for an 8-bit architecture.

author: lod
author_rank: Contributor
timestamp: March 30, 2016, 03:35:04 am
content: Quote from: andyturk on March 30, 2016, 03:23:50 amThere is a per chip royalty for every ARM core, which is significant in the cent per processor market.As for programmer/developer time, 8 bit systems are great. They are well known, there are solid libraries and code examples. The development cycle is simple so you are up and running quickly.And finally because the chips are fairly simple and well understood you can play really interesting games - I once bounced the power rail of an ATTiny to induce noise to the ADC process - these become harder with bigger more complex chips.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 30, 2016, 03:50:47 am
content: I use a lot of 8bit AVR's for light-weight distributed tasks. The system I have designed (starting a while back now), has a bunch of smallish tasks that I wanted to be totally isolated compute-wise from other tasks. They are also in modules that can be removed and replaced in hot-swap with only a few pins available to connect. I don't need the compute power, like the low power when they are running and each one can sleep independently. All the code is in place and I keep adding to it, but don't want to start over. 16bit and 32bit MCU's will not help this application in the end - so 8bit will continue to go in it.For a future project, I am planning for more horsepower and will be considering 32bit options with better A/D options, ethernet, USB3 and other things that 8bit MCU don't have. 8bit will be around for a very long time - at least as long as coffee makers, garden timers, and other simple cost sensitive products are being produced.

author: mos6502
author_rank: Frequent Contributor
timestamp: March 30, 2016, 03:51:20 am
content: How about, no needless complexity?Look at the errata sheets of most ARMs. They're several pages long. Most 8-bits on the other hand have very few bugs, if any.An 8-bit CPU is much easier to understand. Meaning, a single person can know the entire CPU, the internal timing, etc. On that basis, an expert can predict exactly how that CPU is going to behave. Programming in assembler, he has full control of every aspect of the system.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 30, 2016, 04:10:05 am
content: Quote from: mos6502 on March 30, 2016, 03:51:20 amGood point.For my products, I do:ConceptSystem DesignMechanical EngineeringCNC programming/setupElectrical EngineeringPCB LayoutPurchasing (500+parts/assembly)AssemblyAll testingSales/Marketing....and of course all the software design and coding.I do appreciate the simplicity of my little system. There is enough on my plate. Looking forward to getting an assistant now that I am selling things.

author: ade
author_rank: Unknown
timestamp: March 30, 2016, 04:19:38 am
content: QuoteHe's not talking about the licensing cost alone. He's talking about total ARM "tax" over 8-bit including royalties and having to use more expensive process.Besides, just that $40K can buy well over 1millionof those 8-bit sound chips. Go to Alibaba you will find fully assembled greeting card sound modules (including chip, pcb, speaker, battery) for 10 cents or less.

author: bson
author_rank: Unknown
timestamp: March 30, 2016, 04:28:21 am
content: 8051 has advantages in the number of vendors it can be sourced from. But otherwise, there's no advantage to an 8 bit processor over 16 bit anymore. There's no difference in low-power modes, pin count, price, etc. An MSP430G2553 costs a dollar or two. It's also MUCH easier to program and compile for than say PIC18; TI calls it a RISC processor, but the instruction set and highly orthogonal addressing modes are reminiscent of the pdp-11 more than anything else. The instruction JUMP xxx for instance is just shorthand for MOV xxx,PC. It's like night and day compared to a PIC.

author: Zbig
author_rank: Frequent Contributor
timestamp: March 30, 2016, 04:45:35 am
content: Quote from: bson on March 30, 2016, 04:28:21 amI'm not sure that's really that fair to make a 8051 dinosaur representative of all the 8bit micros. There are non-fossil 8bit cores out there, you know...

author: rx8pilot
author_rank: Super Contributor
timestamp: March 30, 2016, 05:13:28 am
content: Do 8051's have A/D, D/A, UART, I2C, SPI, USB on chip?

author: ade
author_rank: Unknown
timestamp: March 30, 2016, 05:36:59 am
content: QuoteYes:http://www.keil.com/dd/chip/3861.htmIf you order enough of them, they'll put in whatever peripheral you want

author: bson
author_rank: Unknown
timestamp: March 30, 2016, 05:43:50 am
content: Quote from: Zbig on March 30, 2016, 04:45:35 amAVR? Special instructions to fetch a constant from program memory...

author: ade
author_rank: Unknown
timestamp: March 30, 2016, 05:55:42 am
content: QuoteWell you can get 32-bit Cortex M0s starting from 35 cents...But were talking about3 cent8-bit chips here (see video above). Can't bring up a $1-$2 chip and say there's no price difference!

author: digsys
author_rank: Unknown
timestamp: March 30, 2016, 06:06:39 am
content: Quote from: mos6502a BIG +1These days I use the Silabs 8051 derivatives, and I code in assembler. So very easy and simple to use, and with all the extra hardware on board,I can achieve quite complex tasks. I get a buzz from the sense of achievement in how far I can push these suckers, something I guess is lost in the newer age folks.I won't bore you with what we had to work with 30+ years ago :-) .. and yes, I walked 20 miles to school ...

author: mikerj
author_rank: Super Contributor
timestamp: March 30, 2016, 07:10:16 am
content: Quote from: mos6502 on March 30, 2016, 03:51:20 amOf all the micro's I used, Microchip PICs tend to have the greatest number of errata, and worse still new revisions often don't fix existing errata or introduce some of their own.

author: coppice
author_rank: Super Contributor
timestamp: March 30, 2016, 07:15:10 am
content: Quote from: mikerj on March 30, 2016, 07:10:16 amIf you want to see some really nasty errata documents, try the numerous thrown together ARM7 based MCUs which various companies, like Philips, produced just before the Cortex family was launched.

author: tooki
author_rank: Super Contributor
timestamp: March 30, 2016, 11:01:17 am
content: Quote from: little_carlos on March 30, 2016, 12:03:38 amTime to re-watch this episode:In it, Dave discovers it uses a4-bitmicrocontroller. Why? Cuz they get the job done, are insanely cheap, and use less power. Not every application of a microcontroller requires computing oomph.

author: janekm
author_rank: Unknown
timestamp: March 30, 2016, 11:19:35 am
content: Holtek make an 8-bit micro with built-in 24-bit ADChttp://www.holtek.com/english/docum/8bit_Flash_MCU/67f5630.htm

author: wraper
author_rank: Unknown
timestamp: March 30, 2016, 11:22:22 am
content: Quote from: Zbig on March 30, 2016, 04:45:35 am8051 is not fossil. There are 8051 implementations which will beat every 8 bit AVR and PIC in performance and power consumption, and have some very interesting peripherals too.

author: digsys
author_rank: Unknown
timestamp: March 30, 2016, 12:00:30 pm
content: Quote from: janekmAs do Silabs -C8051F350 24-bit, 8-ch., 1 ksps QFP32C8051F351 24-bit, 8-ch., 1 ksps

author: danadak
author_rank: Super Contributor
timestamp: March 30, 2016, 12:07:47 pm
content: How about a micro with lots of analog and a choice of 8051 or ARM M0 or ARM M3core ? 12 bit SAR or 20 bit DelSig, digital filter block....Some of the IP (and you can create your own modules) attached.http://www.cypress.com/products/32-bit-arm-cortex-m-psocRegards, Dana.

author: madires
author_rank: Super Contributor
timestamp: March 30, 2016, 12:30:59 pm
content: Quote from: bson on March 30, 2016, 05:43:50 amThere's no perfect MCU. Any MCU family has some pros and cons. Simply pick the one suited best for the job.

author: madires
author_rank: Super Contributor
timestamp: March 30, 2016, 12:48:00 pm
content: 8 bit MCUs are also a good starting point for learning about MCUs. If everyone would start with an ARM and embedded linux we would get a lot of bloatware.

author: EEVblog
author_rank: Unknown
timestamp: March 30, 2016, 01:11:17 pm
content: Quote from: bson on March 30, 2016, 04:28:21 amA whole DOLLAR?

author: coppice
author_rank: Super Contributor
timestamp: March 30, 2016, 01:15:33 pm
content: Quote from: janekm on March 30, 2016, 11:19:35 amThere are a number of small MCUs with 24 bit ADCs, mostly made for the energy meter market - see TI, Maxim, Prolific, Vangotech, etc.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 30, 2016, 04:34:57 pm
content: Quote from: janekm on March 30, 2016, 11:19:35 amI had no idea, never had them on the research list. Development speed is very important to me, so I would be looking at the dev tools even closer than the hardware. Nice to learn of an option that I did not know about though.

author: danadak
author_rank: Super Contributor
timestamp: March 30, 2016, 04:43:44 pm
content: If you look at the Cypress PSOC there are parts well under $ 1, M0core, all 32 bit parts, as well as M3 core ~ $4. What other vendors do nothave is a rich library of analog (more than just A/D), routability ofconnections and modules, on chip .1% reference, DSP capability,and tools excellent, GUI based, and support both C and Verilog (for thespecial HW you want to design).Core ARM based cores, mainstream of industry now. Both in ASIC,FPGA, as well as standalone. Cores are ARM M0, M0+, M3, all 32bit cores. And one family 8051 core.Tool is called PSOC Creator. Many basic and advanced videos to learnfrom.http://www.cypress.com/video-libraryRegards, Dana.

author: lapm
author_rank: Frequent Contributor
timestamp: March 30, 2016, 05:07:06 pm
content: 8-bitters are still around simply because you don't always need something more powerful. Simple toys, meteor lights, etc are just perfect for slow 8-bit cores...