eeprom chips

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nyanberrycake
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Joined: Mon Mar 30, 2020 4:35 pm

eeprom chips

Post by nyanberrycake » Mon May 04, 2020 3:32 pm

im starting my dev cart. I know i need 32kb of program rom. Id like flash rom like the AT29C256. Easy to find. except there are a ton of markings after each chip I look at like 90PC 90PI Dip-28, among many many others. I can't seem to find what these markings even mean. I have found a lot of those chips on ebay, but they all seem t have differing suffixes. any help?

lidnariq
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Location: Seattle

Re: eeprom chips

Post by lidnariq » Mon May 04, 2020 3:43 pm

nyanberrycake wrote:
Mon May 04, 2020 3:32 pm
except there are a ton of markings after each chip I look at like 90PC 90PI Dip-28, among many many others. I can't seem to find what these markings even mean. I have found a lot of those chips on ebay, but they all seem t have differing suffixes. any help?
"90" = 90ns, the amount of time from when /CE its goes low to when the output would be valid. (NES PRG ROM needs anything faster than 350ns. NES CHR ROM needs anything faster than 280ns.)

"DIP", the shape of the package.

28 - the number of pins

"P" - in this case, DIP

"C" or "I" - "commercial" or "industrial" temperature range.

Garth
Posts: 174
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Location: Southern California
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Re: eeprom chips

Post by Garth » Tue May 05, 2020 11:49 am

nyanberrycake wrote:
Mon May 04, 2020 3:32 pm
I have found a lot of those chips on ebay
Be careful! If they're coming from China, they're usually not what they say they are. We've been through this on the 6502.org forum. Recently there have been a lot of fake 6502's and 65c02's on eBay—fake in the sense that they're not the exact type, brand, or date that they're marked. Ed started a topic about it, "Bargain chips bought online - buyer beware!" which you'll want to check if you're tempted by the lower prices. Take a look at the Chinese counterfeit IC market:
https://www.youtube.com/watch?v=j9nasajve1o
https://www.youtube.com/watch?v=5vN_7NJ4qYA

I would recommend buying only from legitimate distributors like Jameco, Mouser, and Digi-Key.
http://WilsonMinesCo.com/ lots of 6502 resources

Ice Man
Posts: 530
Joined: Fri Jul 04, 2014 2:34 pm

Re: eeprom chips

Post by Ice Man » Wed May 06, 2020 1:26 am

I have been buying from China (Aliexpress) for years and never had any counterfeits or non working parts.
Sure, there may be one defective unit out of of hundred but overall I've been satisfied 99.9% of the time.
This is for EPROMs and Flash ICs btw.

nyanberrycake
Posts: 5
Joined: Mon Mar 30, 2020 4:35 pm

Re: eeprom chips

Post by nyanberrycake » Wed May 06, 2020 3:53 pm

lidnariq wrote:
Mon May 04, 2020 3:43 pm
nyanberrycake wrote:
Mon May 04, 2020 3:32 pm
except there are a ton of markings after each chip I look at like 90PC 90PI Dip-28, among many many others. I can't seem to find what these markings even mean. I have found a lot of those chips on ebay, but they all seem t have differing suffixes. any help?
"90" = 90ns, the amount of time from when /CE its goes low to when the output would be valid. (NES PRG ROM needs anything faster than 350ns. NES CHR ROM needs anything faster than 280ns.)

"DIP", the shape of the package.

28 - the number of pins

"P" - in this case, DIP

"C" or "I" - "commercial" or "industrial" temperature range.
Awesome, great info thanks. I checked on both of those sites and they're not selling those chips anymore. I saw some 27c256 chips but those arent reburnable (from my research). Where are people buying these chips? is there a contemporary model?

lidnariq
Posts: 9379
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: eeprom chips

Post by lidnariq » Wed May 06, 2020 4:16 pm

At least for purchasers in the US, only Microchip=Atmel=SST and Greenliant are still making new inexpensive 5V programmable ROMs. (Other vendors exist, but their prices are lackluster, and often don't come in DIP). This may not be true in other countries, but I can only speak to what I see.

So between all those constraints, for all-new 5V DIP parts, you're basically stuck with just Greenliant's GLS27SF(512 / 010 / 020) and GLS29EE(512 / 010), and Microchip's SST39SF(010A / 020A / 040) and OTP AT27C(256 / 512 / 010 / 020 / 040 / 080).

"27C" doesn't necessarily require that the result not be reprogrammable. Some of them - although not any new ones now - have a quartz window that expose the silicon inside, and a UV light can erase them. Or you could decap an OTP ROM so that you can get some UV light in to erase it

You might find Octopart useful. Or maybe accept used parts.

nyanberrycake
Posts: 5
Joined: Mon Mar 30, 2020 4:35 pm

Re: eeprom chips

Post by nyanberrycake » Thu May 07, 2020 4:01 pm

lidnariq wrote:
Wed May 06, 2020 4:16 pm
So between all those constraints, for all-new 5V DIP parts, you're basically stuck with just Greenliant's GLS27SF(512 / 010 / 020) and GLS29EE(512 / 010), and Microchip's SST39SF(010A / 020A / 040) and OTP AT27C(256 / 512 / 010 / 020 / 040 / 080).
Thank you friend. I did a lot of research on chips and yes, 28c is also electronically reprogrammable and I found a lot of chips for under $10. I found a lot of misinformation on EEPROMs but I found (and bookmarked) a good resource.

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