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AT29C040 flash chip noise problem

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AT29C040 noise problem

Has anyone had any experience in using AT29C040 flash chip. I have designed this 2 layer board with an 8051 CPU, a 62256 RAM and 4 x AT29C040 flash for a total 2MB fash storage. The problem is that the 29C040's return erroneous data once in a while resulting is system upsets. Removing the flash from the socket and running the system without any Flash (after some software modifs) delivers a problem free performance
 

do you use a 100 nF capacitor for decoupling all chips? the 8051 and the flash.
may be that you need pull-up or pull down r/w linees to avoid errouns cycles in the flash.
bye G.
 

Yes I have generously used 0.1uf ceramic caps taking care that they are electrically very close to the chips. The 2 layer board is design for short and thick ground and Vcc tracks and all the usual stuff. The problem is that the 62256 RAM on the same bus never gives any problems and the FLASH does.
 

At what speed are you accessing the '040s?
 

hi techie,
could it be that your 8051 can not drive the adress/data bus with 4x FLASH
and 1x RAM?
can you try with 1x FLASH and 1x RAM?
 

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