Author Topic: Switching device address lines of I2C EEPROM?  (Read 1422 times)

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Offline c4757p

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Switching device address lines of I2C EEPROM?
« on: February 16, 2015, 05:55:11 am »
I'm working on a system with multiple cards on a backplane, and I'd like to put a small EEPROM on each one to identify the card and, in some cases, provide some calibration memory for it. The easiest seems to be the usual cheapo I2C EEPROMs. Problem is - with six slots, I can't assign all of them an address (even if they had enough address lines - some do, though most have only two - I don't have the available pins on the backplane). I do have one line available on each slot that I could use to individually address its EEPROM. Obviously, I could put a switch on the I2C lines to completely gate them, but it might be easier.

Can I just tie this line to one of the address bits, so that only the selected device will respond to the address I call out? That is, changing the device addresses and calling out the same address, rather than keeping the addresses static and calling out different addresses. None of the datasheets seem to indicate whether there is any latching on those pins, or for that matter anything resembling a delay after changing their values, because they obviously don't intend you to do this. But can you?
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Offline hamdi.tn

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Re: Switching device address lines of I2C EEPROM?
« Reply #1 on: February 16, 2015, 07:11:11 am »
it's seem totally possible to me, anyway i simulated that with 24LC512 and it work.
 

Offline Christopher

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Re: Switching device address lines of I2C EEPROM?
« Reply #2 on: February 16, 2015, 06:23:46 pm »
Why not bring the address lines out to the backplane and set each backplane connector an address? :-//
 

Offline c4757p

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Re: Switching device address lines of I2C EEPROM?
« Reply #3 on: February 16, 2015, 06:25:18 pm »
Lack of pins, I said that. I'm trying to "abuse" an existing control signal so I don't have to find space for some more pins if I don't have to.
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