Getting 128Kx8 EEPROM
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!
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!
Comments
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
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
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.
Post Edited (nick112147) : 3/6/2008 1:45:14 AM GMT
Thanks for the help.
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.
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.
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.
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
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.....