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Double-even reads from HM628128ALP EEPROMs
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Aggressive_Doughnut:
I arbitrarily grabbed a tube of HM628128ALP EEPROMs from the shelf, slapped one in my little arduino-based programmer, and gave it a quick test and... oddly... I get no odd values read from the ROM in my little displayContents table, instead I get the data from address 0 showing for both address 0 and address 1, the data from address 2 for both 2 and 3, and so on:
000: 2a 2a 0d 0d 2f 2f 34 34 39 39 1a 1a 14 14 0c 0c
...
When I read the odd values outside of a loop, they all read fine. After a while of fooling around I split the ROM-reading loop into an even loop and an odd loop and everything works great.
Has anyone ever seen this before? I don't see it as a "feature" in the datasheet anywhere. I get this for all of my HM628128ALPs but not other EEPROMS.
Deni:
HM628128ALP is SRAM, not EEPROM isn't it? Although that should not affect reading...
newbrain:
Yes, it's a 16kB CMOS static ram (neither ROM nor EEPROM).
As the programmer is self built, and I presume coded: is it complying with the needed setup and hold times (i.e. CSx, OEn or address to data read)?
Is the A0 connection good and low resistance?
Can you check signal integrity with a scope?
Which speed grade are those RAMs?
amyk:
Check the configuration of the A0 pin. If it is set to open-drain (maybe with only the internal pullup enabled) then this behaviour is possible.
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