Is it possible that embedded system doesn't have flash memory? If we use flash memory in embedded system, then we don't need to use ROM, or both? My understanding is that flash memory is similar to ROM, that stores permanent data like boot up instructions?? Is that correct? Please advice. thanks...
I think some form of non-volatile memory is needed in a system of any complexity. I can picture an ASIC or CPLD that does something useful yet has no non-volatile memory. Like a sound effect generator, one button switches sounds, the other button turns sound generation on.
The non-volatile memory doesn't need to be flash. It can even be SRAM with battery backup.
Flash memory is rom, it's just programmable in circuit by the circuit/system itself.
-Dave
-- David Ashley http://www.xdr.com/dash Embedded linux, device drivers, system architecture
If the embedded system doesn't have flash memory, how can it boot up?? I keep thinking flash memory or ROM is used for boot up process.
is that true? please advice more....
Why flash? Why not a rom? Eprom. EEprom. Serial rom. CPLD. Compact flash. ACE. If you need more information than can be stored in the raw logic of the device(s), then you need some other form of non-volatile memory. Where's the mystery?
An embedded system doesn't necessarily need a cpu. Or an OS.
-Dave
-- David Ashley http://www.xdr.com/dash Embedded linux, device drivers, system architecture
ROM is not necessarily Flash. Flash is just a convenient method of being able to reprogram ROM chips. In the old days ROM consisted of fuses that were blown so the data was permanently etched into the memory. Later on erasable ROMs became avaiable but you had to shine UV light on them to clear.
Speaking to a very old hairy-eared engineered once he told be that the ROM he used many many years ago was windings of copper wire with ferrite beads on them to represent data. Apparently they always used women to wind the wires because they were more accurate than men. But I digress....
As long as there is some kind of memory available to the processor that is not lost when the power is removed (so it is non-volatile) then it will be able to boot. Flash is one type of possible memory (and the most common) but so is battery backed Static RAM or an old-school PROM or a number of other methods.
You wasted far too much time on this answer. The correct response was "The answers to your homework can be found in the reading list provided by your professor".
It's not often someone asks a question I know the answer to :-)
I don't think the students are back yet are they? The UK ones only put down their burger flippers on Sunday and are still too drunk to post on usenet.
US students have been back at school for at least two weeks. (My wife is a seventh grade teacher, and I'm back at college myself... so I know these things).
My girlfriend is now in her second week as a newly qualified maths teacher. Unfortunately, she has little time to do anything else so all our conversations must be about what the little buggers have been up to this week. I guess this must be revenge for the time I spend disseminating the virtues of my GP2X to her ;-)
What is a GP2X?
Here it is:
-Isaac
You got a GP2X? Cool! I wanted one of those but I decided instead to blow my money on a Palm Zire 71. Did you code for it? How is coding for it? A 200Mhz ARM9 might be good enough for a software 3D implementation maybe even a lot more. Though I believe the GP2X has a hardware blitter so it may help ease some load.
-Isaac
Holy cow, it wasn't THAT long ago; I did a lot of transformer ROM re-wiring (to change code). --Still have devices running using transformer ROM.
Most transformer ROM used U-cores so that the assembly can be easily opened for maintenance (rather than torroids).
Regards,
Michael Grigoni Cybertheque Museum
Is that another phrase for rope memory?
-- Some informative links: news:news.announce.newusers http://www.geocities.com/nnqweb/ http://www.catb.org/~esr/faqs/smart-questions.html http://www.caliburn.nl/topposting.html http://www.netmeister.org/news/learn2quote.html
One might boot from a serial line, a network routed message, a r/f or optical signal. It might have a ROM or FLASH internally to do this, but devices can be hard wired to do any of the above without any ROM or FLASH or non-volatile programmable memory in them.
When you're working at the cutting edge then two weeks is a long time ago ;-)
That wiki that Isaac posted a link for will tell you the facts. In my opinion it is both a good product and a good idea - basically a linux based open source PSP with a major appeal to retro gamers due to the wide variety of emulators available.
I mainly use mine to watch movies on the train to/from work but I also play games on it too - quake is particularly and I have become re-addicted to Rick Danderous on the Amstrad CPC464 emulator.
It is still a little raw yet but with some concerted developer effort then it could become a real giant-killer. However, they need to get the power management sorted because, even with 2x2500mAh batteries it still goes through them in just over a movie.
How is the Zire? Was it the right decision? I'm delighted with my GP2X but would like a bit more battery life - it doesn't appear to have any power management at all. The chap who did all the power management for the Fedora Core distribution is a good buddy so I've been bribing him with beer and curries to see if he can put some time into GP2X power management. He's back at university now so he should have plenty of time available ;-)
I haven't coded anything for it yet because I've been struggling to find any time. I need to master video conversion and processing before I can get into any coding though. The GP2X needs a really good stable movie player than can handle a lot of formats because the standard one is a bit limp. I've tried mplayer on it but never managed to get it to play anything at all.
There are 2 ARM9's in use and I believe one is for thinking and the other is purely for handling graphics so there should be enough power available for a bit of 3D - that would be a very interesting project and might be something I could fancy having a crack at.
I worked with ARM a good bit so I'm fairly comfortable with the processors but I have never coded for Linux before so I have a pretty steep learning curve. This is the main reason I bought the GP2X (other than for watching the Sopranos on the train) because I think I'll be using Linux in my next product and I want to learn how to use it in plenty of time. Also once I get the hang of Linux properly then I can finally be shot of Windows, for which my patience is dwindling - how many iterations of Outlook do they need to get it right?
Some of the old mainframes had absolutely no ROM. When you boot them, you have to code in the machine code instructions using a set of DIP switches until you've got enough to start booting (from disk, tape, punch card, or whatever). Fortunately, these things were seldom switched off.
Why would you need any special ROM for the boot loader in any computer prior to about 1975 ? These old computers had core memory, so there was not a problem switching these off, they would just continue from where the power was lost, after the power was restored.
Thus the boot loader code would also remain in memory during a power failure. Only if some accidently overwrote the boot loader code, it would have to be entered manually with the front panel toggle switches (perhaps 10-20 instructions), so that the disk driver could be loaded from a paper tape.
To avoid the accidental overwriting of the boot code, some computers had some circuitry to prevent accidental overwriting the address range where the boot code was by programs gone mad, but unfortunately, this did not always work and you had to enter the boot loader manually :-). Paul
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.