rrw@naucse.cse.nau.edu (Robert Wier) (01/26/91)
A research group I'm involved with needs to put together a
data logging system in a relatively short time. We have a
number of single board computer systems which might fill the
bill (one has 256K memory - sufficient for 80 days of readings
or so), but it only has SRAM. The research site is remote
(out on the reservation, near Window Rock on the NM and AZ
border), so we'd like to go out there and leave it to record
data for at least a month unsupervised. But we are concerned
that dead batteries or other diasasters might cause us to lose
ALL the data we've accumulated. One possible solution is what
Dallas Semiconductor calls Intelligent Sockets. These are
IC sockets which come with a lithium battery built in, which keep
the memory chip powered up if the main vcc fails. The stated
life is between 5 - 10 years, depending on the chip selected.
Alternately, they make actual memory chips with the battery
built in (they call 'em non-voltile RAM).
I'd be interested in hearing from anyone who has knowledge about
or has used these, price range, etc...
Please either E-mail or post here.
THANKS
- Bob Wier
-------------- insert favorite standard disclaimers here ----------
College of Engineering
Northern Arizona University / Flagstaff, Arizona
Internet: rrw@naucse.cse.nau.edu | BITNET: WIER@NAUVAX | WB5KXH
or uucp: ...arizona!naucse!rrwftpam1@acad3.alaska.edu (MUNTS PHILLIP A) (01/28/91)
In article <3222@naucse.cse.nau.edu>, rrw@naucse.cse.nau.edu (Robert Wier) writes... [query concerning Dallas NVRAM's and SmartSockets delete] > I'd be interested in hearing from anyone who has knowledge about > or has used these, price range, etc... I have worked with the NVRAM's from Dallas Semiconductor (and Thomson-CSF also). Prices for small quantities are in the $20.00 range, depending on density and speed. The SmartSockets are cheaper, but you have to add in the cost of the RAM. Dallas Semiconductor devices can be ordered by credit card for overnight delivery at 1-800-336-6933. Product info may be requested from 1-214-450-0969. All of these devices (and EEPROM's as well) share a common problem: the microprocessor accessing them can go berzerk on power-up and especially power- down conditions. I have even seen this with serial EEPROM's that have an extremely complicated access protocol. The Motorola 68HC11 single chip microcomputer with internal EEPROM also suffers from this problem. The only solution is to make sure the microprocessor is reset whenever its supply voltage is out of tolerance. This requires special low voltage detectors; circuits based on op amps or comparators and Zener diodes are not accurate enough. They company I worked for at the time was unwilling to pay for the low voltage detectors and they have suffered from product unreliability to this day. (I still do software for them on a contract basis.) I liked the 5 terminal regulators that SGS and now National Semiconductor make; the low voltage detector is on the same die as the regulator so everything should track with temperature, etc. These regulators have a pin for a capacitor and a pin to reset the micro whenever the output voltage is out of tolerance. My prediction is you will need to retro fit this sort of protection circuit into your system if you intend to use NVRAM's or SmartSockets. Philip Munts N7AHL NRA Extremist, etc. University of Alaska, Fairbanks
danr@ais.org (Daniel Romanchik) (01/29/91)
In article <3222@naucse.cse.nau.edu> rrw@naucse.cse.nau.edu (Robert Wier) writes: > > A research group I'm involved with needs to put together a > data logging system in a relatively short time. We have a > number of single board computer systems which might fill the > bill (one has 256K memory - sufficient for 80 days of readings > or so), but it only has SRAM. The research site is remote > (out on the reservation, near Window Rock on the NM and AZ > border), so we'd like to go out there and leave it to record > data for at least a month unsupervised. But we are concerned > that dead batteries or other diasasters might cause us to lose > ALL the data we've accumulated. One possible solution is what > Dallas Semiconductor calls Intelligent Sockets. These are > IC sockets which come with a lithium battery built in, which keep > the memory chip powered up if the main vcc fails. The stated > life is between 5 - 10 years, depending on the chip selected. > Alternately, they make actual memory chips with the battery > built in (they call 'em non-voltile RAM). Another possible solution is to dump the data to an external device if your single-board computer has a serial port. ADPI (phone 513-339-2241) makes a line of floppy and tape drives with RS232 interfaces. Don't know if they have battery-powered units, but I wouldn't be surprised if they do. Good luck, Dan (danr@ais.org)
ltf@ncmicro.lonestar.org (Lance Franklin) (01/29/91)
In article <1991Jan28.083000.28601@ims.alaska.edu> ftpam1@acad3.alaska.edu writes: }In article <3222@naucse.cse.nau.edu>, rrw@naucse.cse.nau.edu (Robert Wier) writes... } }[query concerning Dallas NVRAM's and SmartSockets delete] } } All of these devices (and EEPROM's as well) share a common problem: the }microprocessor accessing them can go berzerk on power-up and especially power- }down conditions. I have even seen this with serial EEPROM's that have an }extremely complicated access protocol. The Motorola 68HC11 single chip }microcomputer with internal EEPROM also suffers from this problem. I beleive Dallas Semiconductor has a solution for this as well... Their MicroMonitor chip (DS1232) monitors the power status via a "precision temperature compensated reference and comparator circuit". An out-of-tolerance condition generates an internal power fail signal and forces reset to the active state. A return to in-tolerance condition keeps the reset signal active for 250ms to allow the power supply and processor to stablilize. It also includes a debounced input for a reset switch and a watchdog timer that will reset the processor if it's not pinged at a given interval (150ms, 600ms or 1.2seconds). Voltage tolerance is settable to either 5% or 10%. Another chip, the Power Monitor (DS1231) is similar, but will provide a warning before hitting reset, doesn't have the watchdog timer or reset switch circuitry and is evidently designed to replace standard power-up reset circuitry. Lance -- Lance T. Franklin +----------------------------------------------+ (ltf@ncmicro.lonestar.org) | "You want I should bop you with this here | NC Microproducts, Inc. | Lollipop?!?" The Fat Fury | Richardson, Texas +----------------------------------------------+
aw0g+@andrew.cmu.edu (Aaron Wohl) (02/01/91)
Dallas is a good company to work with. They have a credit card sales dept that sells small quantities shipped overnight. There number is 1-800-336-6933. So far I have only worked with the DS2250T-64-16. This is a small 40pin simm chip. It has an 8051 compatable microprocessor, a clock and 64k of non volitile ram. The all the memory and clock run off a flat pack lithium cell for 10 years. If you raise PSEN* to 5v and bring RST to ground it autobauds on the serial input. There is a system loader to send intel hex files and dump memory and such. Once loaded the program is write protected. It is really great to do development without hasseling with eproms, also since the external bus isn't needed ports P0 and P2 are freed up for IO. I wirewraped a circuit on sunday and it works great. The only problem I had was forgeting to pull EA* high and it wouldn't st I just got 6 model 90-1230Y-100 100ns battery backed up 32Kbyte static ram from them for $30 each and a couple of 8kbyte rams (90-1225D-100) for $17 each. I haven't hooked them up yet so I don't know any problems to look for. Some other dallas products that look like fun (untried by me!): DS5000-TK 8051 compatibale with 8kbyte to 32kbyte batter backed up ram and real time clock in a 40pin socket compatable with 80C51. Software for pc to download and cable and in circuit download cable. DS2167K Adaptive data compression design kit - play with compressed audio DS6417 256kbit to 4megbit nonvolitle serial access ram in a package about the size of a credit card.
nagle@well.sf.ca.us (John Nagle) (02/03/91)
> All of these devices (and EEPROM's as well) share a common problem: the >microprocessor accessing them can go berzerk on power-up and especially power- >down conditions. I have even seen this with serial EEPROM's that have an >extremely complicated access protocol. The Motorola 68HC11 single chip >microcomputer with internal EEPROM also suffers from this problem. > The only solution is to make sure the microprocessor is reset whenever Yes, the M68HC11 is particularly prone to this problem, enough so that there's a Motorola application note on it. The M68HC11 has the unusual property that as the supply voltage drops, the processor stops branching but continues to execute instructions. So, for a few milliseconds, the processor cycles through its 64K address space, executing every word in the machine as an instruction. If there are any instructions in memory that write EEPROM, trigger peripherals, or do something obnoxious that can still be done with power failing, they will be executed. Since this part is intended as a single-chip microcontroller (it has an A/D, timers, and such) for minimum-parts-count applications, it really should have had the appropriate on-chip circuitry to prevent this. But it doesn't. Motorola recommends adding circuitry to detect power-low and force RESET until power falls to the point that the clock stops. John Nagle