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Flash memory access problem - please help

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bobcat1

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Hi

I'm trying to access AMD FLASH AM29f080B-90 memory and it's dosen't

work well :

1) access to flash is working from time to time e.g one time i can access and read the menufecture ID and on time I can't read it

2) Programing is the same


My logic analyzer show 100nS access pulse for Read Write and CS


I think the problem relay to access time - ?



thanks


bobi
 

mr_ghz

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Hi bobcat1,

How do you access this flash? By a CPU? What type?
It could be possible that you have an address change during the WR/CS
pulse or a spike on your VCC line. Do you have decoupling capacitors?

Bye
 

bobcat1

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Yes I do Access the flash using a philips XA cpu

Yes I do Access the flash using a philips XA cpu oprating @ 20 Mhz

To access the Flash I'm using an address decoder programed on cypress

cpld

Yes i do have decupling cup's on every chip vcc -> gnd .


bobi
 

hqqh

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flash access

hello,
can you read any data? do you have two flash devices in parallel to reach 16bit bus-with. then you have to be care for the adresses you send to the flash (you have to double the adresses).
if you have an logic analyzer, check wether the cpu sends the correct unlock cycles (if you want to read device id or during programing).

greetings,
hqqh
 

mr_ghz

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Hi bobcat1,

Check (with oscilloscope or logic-analyzer) if the setup and holdtimes
are met. Probably there is a problem with the propagation-time inside
your address-decoder.

Bye
 

bobcat1

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I'm using an 8 bit wide data bus and a single flash chip

I'm using an 8 bit wide data bus and a single flash chip in the system

I also have an external uart 16c552 and extenal ram and it's working

very well , e.g. Accessing the RAM & the UART work without ant system

error's

the problem is only with the flash memory

bobi
 

DaMa

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You should disable all of any interrupts during Flash memory access (read and write).
 

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