In search of bad 4164, 41256 DRAM

Hi All,

 

I built a DRAM tester for fun and to brush up on Arduino development. I have
a lot of students I work with use Arduino, so I wanted to build something to
stay up to date and I have not done anything with an Arduino for more than a
year. I found a project online as a starting point and added an automatic
DRAM refresh driven by Timer2 overflow. Even with a pokey Arduino and the
ISR in C it can refresh 64 rows in less and 100us. 

 

I did a quick test with a 41256 just now and was happy I could read/write
all bits successfully. Then I realized I don't have any known bad 4164/41256
type DRAM chips on hand. So, if you happen to have a few bad DRAM chips on
hand and you're in the USA I would gladly take them off your hands.
Otherwise I'll have to figure out a way to inject a simulated fault. Maybe
writing a wrong value to a known cell after writing the proper pattern to
all cells would be a good enough simulation?

 

I still have a way to go with the software. The original project I found
online used separate functions for each test pattern. I want to create a
single function that will write a bit pattern that is passed to it and then
verify that pattern is in memory. Maybe a n second pause would be good to
have in place between the write and verify to ensure that the refresh is
working properly?

 

Thanks,

Jeff Birt