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Arduino 24c256 Eeprom time to read whole chip

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dr pepper

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Any ideas how long it would take to read the whole 64k in this chip.
Read not write.
I havent got hold of one yet, just working out whether I can just read every location or I need to make some kind of smart search.
 

ronsimpson

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Which 24c256? Some clock at 400khz and some at 1mhz. I see there are many different write times.
I looked at the CAT24C256.
It takes a little time to set up read at 0. But after that it should hand you a byte every 9 clocks. Assuming your CPU can do the speed.
32kx8 If you can clock at 1mhz then it is 9uS/byte. 0.3 seconds. How bad is my math?

Now that I think about it. Set the address to 7fff and the next read will send data for 0.
 

dr pepper

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I dont think the 'duino can address at over 400kc (the i2c peripheral might but I dont think the proc would keep up), the processor would be the limiting factor.
Sequential addressing would speed things up quite a bit.
I think I'll put together a storage regime, putting the data is numerical order, that'll speed it up a lot.
The other option would be parallel access eeprom, but that not very 'elegant'.
 

dr pepper

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If anyone is interested I wrote some code & found out how long it takes to read 16k at 400kc, about 10 seconds.
 

Pommie

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So, to answer your original question - about 20 seconds for the whole 32k.

Why did you only read half of it?

Mike.
 

ronsimpson

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If anyone is interested I wrote some code & found out how long it takes to read 16k at 400kc, about 10 seconds.
That seems real slow.
At 400khz and 9 clocks/byte ...... lets say 10 clocks so I can do the math in my head. You should get a byte at 40khz.
If you read one byte at a time (send the address every time) it will be 1/3 or 1/4 as fast. Maybe 10k bytes/sec.

Next: many compilers are quite slow. They might not do sequential reads. (Arduino is not a compiler .... even more slow)
 

dr pepper

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Looking at it that way your right.
I'm using a library, maybe theres a delay in there somewhere.
Does the job for me though I only need to access one byte at a time so I'm not going to worry about it.

Poms, good point, the chip I have at the moment is a 128 not a 256 I blew that one up on 12v.
 

dr pepper

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So a '128 would take 1/2 that time at about 600ms, that would have been Ok for this project.
Maybe I ought to look for a better library eh.
 

be80be

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There sure not all the same.
The arduino can do the 400khz you have like 10 ways to read one of these you need the newer I2Ceprom library.
 
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