A question about RAM,welcom to discuss

[sunms]

I met a question during my sample test.
In my opinion, a RAM will change its content when you write the data into it.But I found that read option alone will sometimes change the content of the RAM. So could anybody tell me why this happens? Or is this related to the foundary 's RAM?

Thanks!

 

[sp]

hi...dear fren,

could i ask how u find out during read operation, the data do change,,,

it shouldnt change during or after the reading operation, or data receive will b wrong...


regards,
sp

 

[IanP]

If what you say is true, no electronic device with RAM should work reliably ..
Remember, these things are not cleaver at all and if YOU make a mistake (software or hardware) .. BOOM!!!

Back to your case: several issues involved - timing problem (R/W pulse to short, to long, ....), two or more devices accessing data/addres bus at the same time, de-coupling of the (+)Vcc/Vdd line ..... and so on ..

 

[cnspy]

I think it does not need to be discussed. If the value is changed in read process, it must has something wrong. Just check your RAM model or your stimulus to the RAM.

 

[sunms]

Of course it's the read operation causes the change of RAM content!!!

When I synchronize the address signals connected to the chip using the clock that the RAM used. It's OK!

So I can be so sure.

 

[Sparc]

This cannot happen with any RAM, but if it's taking place, as is just said synchronize your operations or You are accidentally writing something into RAM. In big designs, when we deal with number of dedicated RAMs for different components, Synchronizing all of them becomes an issue sometimes.

 

[manaman]

how many ports your ram has

 

[sunms]

Did anyone ever post research paper about RAM?
Thanks!

 

[nitu]

Hi...
What you are asking is that "RAM content changes when you read it !!"..
This is the pratical problem in SRAM .. This can happen when the Noise Margin of the cell is not large and the read operation is sufficient to make it trip....
In case you are interested in the papers you can search for static nosie margin in SRAM cells in case your RAM is Static (6 transistor RAM)

I hope this will help..

 

[sunms]

Hi nitu
Thanks for your help.I found the problem during sample test and it's urgent for me to solve it!
So can anyone post some document?

 

[bg21359]

I think you should make it clear whether the RAM is DRAM or SRAM, or it's actually on-chip cache. There is a big difference between DRAM and SRAM.

Another thing is what it's the speed of RAM you're using. If it's high speed, there is a possibility that your IO timing does not have enough margin which may cause some
wired thing happens.

 

[rprince006]

Yes, I agree with Big21359. First of all, you must know what kind of RAM you are
using, read the datasheet carefully before using it in your system.

If your RAM was not broken, it may be the interface (and/or timing) which caused
the problem.

Cheers,

 

[tutx]

I think that you first check what RAM you are using and its characteristics.
If your RAM changes its values in read operation, it may have faults: either RAM itself or the surrounding circuits.

Hope you pass this problem,

 

[sunms]

Thanks for all your reply.

 

[power-twq]

read operation itself can't change a normal ram's content, your ram

may has been damaged.

I met a question during my sample test.
In my opinion, a RAM will change its content when you write the data into it.But I found that read option alone will sometimes change the content of the RAM. So could anybody tell me why this happens? Or is this related to the foundary 's RAM?

Thanks!