Getting 128Kx8 EEPROM

dnaddor

Hi everyone.

I'm building my first prototype of a product using the Propeller chip. I need the larger SRAM, so I figured I could just go to DigiKey and order an 8-pin DIP Atmel 24C1024, just like the one in my Hydra board.

Only it has been obsoleted, and I can't find anything compatible. The other chips have different pinouts, and probably won't boot the Propeller chip.

If all else fails, I'll have to use 4 32K chips (I can order these from Parallax), but surely there is a better way.

Any ideas?

Thanks!

nick112147

To my understanding ANY chip can boot the propeller, because people use SD Cards and all sorts of things to boot the chip up. Serial EEPROMS using full duplex I/O are reletively inexpensive. 128K serial eeprom:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=24LC128-I/P-ND

DigiKey will even program it for you, if you dont have a programmer. Its pinouts may be different, but from what I have learned, as long as the two serial pins on the Propeller (upon bootup) are connected to a serial EEPROM, it should be okay. I am not 100% sure of this, but I don't think the Propeller design team would limit the chip to such a narrow field of acceptable components. In the chip I provided, just make sure to ground the Address pins (A0-A2) and hook up SCL and SDA correctly.

Hope I helped,

Nick

Bean

Use the AT24C1024B

digikey http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=AT24C1024BW-SH25-B-ND
[noparse][[/noparse]edit] Sorry that is the SOIC version. You'll have to find someone who has the DIP version.

Bean.

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www.iElectronicDesigns.com



Post Edited (Bean (Hitt Consulting)) : 3/6/2008 1:42:02 AM GMT

dnaddor

Thanks for getting back to me so quick.

Unfortunately, I don't think I have the skills or the tools to solder SOIC parts. The available DIP parts seem to be smaller than 128Kx8.

nick112147

That is just the organization, it is organized as eight 16K blocks, totaling to 128K, in the part search it is labeled as 128K(126K x 8). Sorry for the confusion, I should have said something about that. Yes, soldering SOIC's can be a real pain. I myself have never attempted it by hand. Most of the time, unless the person has a really small soldering iron tip, it is done at a manufactoring plant, so ultra-high precision machines do things like that. People do it by hand, but they really, really know what they are doing.

Post Edited (nick112147) : 3/6/2008 1:45:14 AM GMT

dnaddor

Never mind, it's been a long day. I found what I needed in DIP after all.

Thanks for the help.

dnaddor

Well, I'm still not there.

I thought that the 25LC1024 chip was what I needed. It is available in 8-pin DIP, the organization is 128Kx8, but it uses a 3-wire SPI interface instead of a 2-wire interface. Is there a way to use that chip? I can't just connect the input and output together, can I? (I doubt it.)

I specifically need the extra RAM -- 4 times the 32K directly usable by the Propeller chip.

It never occurred to me that there would be difficulty getting the exact same chip that I see used on my Hydra board.

Forrest

Looks like Atmel 24C1024 (DIP) version is in stock at www.jameco.com/ for $6.65.

I'd guess the reason you're having such a hard time locating it is because it's not RoHS compliant - so it was phased out.

dnaddor

You are right about RoHS. Thanks for the tip about www.jameco.com -- that will work great.

I don't know why I didn't find it before, but DigiKey has the Microchip 24AA1025 in 8-pin DIP. It looks like that will work also.

Thanks again for all of the help.

OwenS

Microchip's 24LC1025 should work also. Any 1024kbit I²C EEPROM should be fine, or even something as exotic as a Ramtron I²C FRAM.

deSilva

The Hydra ships with them for a year now... Funny thread this....

Paul Baker

deSilva, the issue isn't finding a part (SOIC versions of the chip as used on the Hydra are readily availible). It's finding a DIP version of the chip, which seems to have been obseleted by Atmel in the RoHS transition. However Microchip still produces them.

One important thing to note between Microchip's and Atmel's chips are that they are only fully compatible for the first 64K bytes, for addresses greater than 64K (the second half of the memory) the two chips no longer conform to the same addressing. For the Microchip part, the sub address in the command byte (those bits used to point beyond 64K) is B0,A1,A0. A0 and A1 are set via the voltage level applied to the A0 and A1 pins. B0 is the bank select and is specified via software. The Atmel chip sub address is A2,A1,P0, so different pins specify the chip's hardware address (pins 2 and 3, while Microchip's hardware address is specified on pins 1 and 2) and Po is the same as Microchip's Bo. So lets say we have an Microchip version and set pins 1 and 2 to gnd, the first 64K bytes has a subaddress of 000 and the second bank is 100. For an Atmel chip with A1 and A2 tied to ground the first 64K has a subaddress of 000, but the second 64K has a subaddress of 001.

What this means is any code written to address to the upper 64K of an Atmel chip would not work for the Microchip chip and vice versa.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Post Edited (Paul Baker (Parallax)) : 3/6/2008 8:06:37 PM GMT

deSilva

I see... my Hydra is a little bit older, so I was not aware it would now come with a SOIC...

Pointing out again the differences between the ATMEL and Microchip version is most creditable... It easily gets lost why one is calling their chip "1025"

I shall try to find the thread where we discussed that addressing before.....