RE: In search of bad 4164, 41256 DRAM

From: Jeffrey Birt <birt_j_at_soigeneris.com>
Date: Sat, 21 Sep 2019 08:16:24 -0500
Message-ID: <002201d5707e$c54a2aa0$4fde7fe0$_at_soigeneris.com>
-----Original Message-----
From: Francesco Messineo <francesco.messineo_at_gmail.com> 

>>A common failure mode is the data I/O pins shorted to a power rail or not >>going to high impedance when the chip isn't addressed. So you must take >>care not to blow the driver pin to the data Input of the chip.

I added the resistors and diode clamps to the schematic last evening and took an inordinate amount of time getting a pleasant looking layout on the schematic. I think good schematics are like good code perhaps both should be pretty to look at 😊. With the three power rails properly current limited I think the diodes should prevent the Arduino from being damaged.

Now I am wondering how to detect a pin not going high impedance. Though I suppose if the chip were in that state odds are it would not function properly otherwise and since I'm testing one chip at a time I don't have to worry about bus contention causing problems.

Thanks,
Jeff Birt
Received on 2020-05-29 22:43:10

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