Author Topic: SRAM: 6C6264 vs 6C62256  (Read 326 times)

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Offline smbaker

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SRAM: 6C6264 vs 6C62256
« on: October 25, 2020, 03:37:31 am »
I have a project that I designed to use either a AS6C6264 or a AS6C62256. I'm only using 4K of the RAM, with the expectation it wouldn't matter which IC is installed.

In my circuit, the following pins differ between the two ICs and this is how I connected them to ensure equivalent behavior:

26 (CE2 on 6264, A13 on 62256): High
1 (NC on 6264, A14 on 62256): High

Everything else (!CE, !OE, !WE, address bits, data bits, etc) is as you would expect for an 8-bit CPU.

Looking at the datasheets (https://www.alliancememory.com/wp-content/uploads/pdf/Alliance%20Memory_64K_AS6C6264v2.0July2017.pdf, https://www.alliancememory.com/wp-content/uploads/pdf/AS6C62256.pdf), my belief is that it should make absolutely no difference which SRAM is used. Both parts are the same speed. Yet it's the case that the 62256 works fine, but the 6264 causes the MCU to sporadically reset, the LEDs to flicker, and general chaos ensues.

Could someone be so kind as to look at the datasheets and see if I have somehow obviously gone wrong?

Thanks,
Scott
 

Offline greenpossum

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Re: SRAM: 6C6264 vs 6C62256
« Reply #1 on: October 25, 2020, 03:58:36 am »
Maybe just a faulty specimen? Do you have any other means to test it?
 

Offline smbaker

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Re: SRAM: 6C6264 vs 6C62256
« Reply #2 on: October 25, 2020, 04:00:14 am »
I tested it in a mini pro programmer and it tested out good (I have no idea how through this test is)
 

Offline greenpossum

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Re: SRAM: 6C6264 vs 6C62256
« Reply #3 on: October 25, 2020, 04:09:32 am »
Can you disconnect that NC? I know it should mean there is nothing connected to this pin but sometimes it can mean don't use this pin.
 

Offline smbaker

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Re: SRAM: 6C6264 vs 6C62256
« Reply #4 on: October 25, 2020, 04:31:17 am »
Can you disconnect that NC? I know it should mean there is nothing connected to this pin but sometimes it can mean don't use this pin.

Yeah, I already tried that... of course, I suppose the IC could have become damaged while it was connected.
 

Offline m k

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Re: SRAM: 6C6264 vs 6C62256
« Reply #5 on: October 25, 2020, 08:07:16 pm »
My first guess is that your CE2 is not very high all the time.
 

Offline smbaker

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Re: SRAM: 6C6264 vs 6C62256
« Reply #6 on: October 26, 2020, 03:32:00 am »
My first guess is that your CE2 is not very high all the time.

I will put the scope on it and find out for sure.

Scott
 


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