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'[PIC]: I2C large eeprom'
2002\01\03@062120 by Carlos Ojea

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Hello:

I found some source code to read an eeprom using master mode i2c, but for
the
adress it use only one byte. ¿How can I access an adress above FF?

Thanks,
Carlos

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2002\01\03@100726 by Simon-Thijs=20de=20Feber?=

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Hello,

Probably this is achieved by page-ing.
Either by sending another address byte or toggling one
of the address pins (A0).


grtz

Simon



--- Carlos Ojea <spam_OUTcarlosojeaTakeThisOuTspamLEVELTELECOM.ES> wrote: >
Hello:
{Quote hidden}

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2002\01\03@104309 by Drew Vassallo

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>Probably this is achieved by page-ing.
>Either by sending another address byte or toggling one
>of the address pins (A0).

Typically, there are 3 block select (or "chip select") pins (A0-A2) that are
used to define the device's address on the bus.  This allows up to eight 2K
devices on the same bus.  For large EEPROMs, these pins are usually not used
externally, but their functionality inside the chip is used.

The EEPROMs are structured to have memory addresses separated into 256-byte
blocks.  For larger memory devices, there are simply more blocks.  To access
a block, use the "chip select" or "block select" bits in the control byte
during a read or write operation.

For VERY large memory devices (more than 256K), the devices simply use HIGH
and LOW address bytes rather than blocks of memory.  I don't know how many
of these devices are on the market as of yet - Microchip's large memory
devices are listed as "Future Products."


I would imagine it would be simple to modify any I2C code to utilize either
multiple blocks or high and low address bytes.

--Andrew

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2002\01\03@104940 by Christian Dorner

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Hi!


>I found some source code to read an eeprom using master mode i2c, but for
>the
>adress it use only one byte. ?How can I access an adress above FF?

This depends on the used chip.

On smaller chips (ie. series 24xx up to the 2416) the hardware address bits
will be replaced by the upper bits of the memory address. On larger chips
(2432 +) you can address the memory by 2 bytes of address (16 bit).

This is maybe not a big help for you due my bad english, so the best will be
to take a look to the datasheets (there a lot on http://www.microchip.com and
http://www.atmel.com for the 24xx series) and you'll see it's easy as pie.


cu, Christian

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2002\01\03@122226 by Carlos Ojea

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>The EEPROMs are structured to have memory addresses separated into 256-byte
>blocks.  For larger memory devices, there are simply more blocks.  To
access
>a block, use the "chip select" or "block select" bits in the control byte
>during a read or write operation.


Ok, but there are only three "block select" bits, so how can I access an
adress above 2K?
For example, using a 24LC16B.

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2002\01\03@124619 by Andre Abelian

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Carlos,

There is a control byte where you specify every thing read, write,
location,
Banks etc.

Andre Abelian



Hello:

I found some source code to read an eeprom using master mode i2c, but
for
the
adress it use only one byte. ¿How can I access an adress above FF?

Thanks,
Carlos

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2002\01\03@125611 by Drew Vassallo

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>Ok, but there are only three "block select" bits, so how can I access an
>adress above 2K?
>For example, using a 24LC16B.

It's possible you're confusing your bits and bytes here.  The 24LC16B has
16K bits of memory, which is only 2048 bytes of memory, or as it's reported:
2K.  There are no "addresses above 2K" on this chip.  Obviously, address
2047 is accessed by using chip select bits "111" and address "11111111".

However, for devices above 2K BYTES (24LC32A, etc.), as I said, they've
added another HIGH byte to the address.  For these devices, the upper 4 bits
of the HIGH byte are zeroes, with the lower 4 bits defining the desired
memory block.  Note that on this particular device, you can once again use
up to 8 devices on a single bus, and the A0-A2 pins are usable.

--Andrew

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2002\01\03@130749 by Christian Dorner

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Hi!

> Ok, but there are only three "block select" bits, so how can I access an
> adress above 2K?

3 block select bits are enogh to address 16 kBit.

> For example, using a 24LC16B.

On a 24x16 the control byte has following meening:

1, 0, 1, 0, P2, P1, P0, R/W

1010 is the "ID" for the EEPROM,
P2-P0 are the upper bits of the memory address,
and R/W stands for Read/Write.

For example to access address 0x456 the

control byte must be "1010100R/W" and the
word address 01010110.

cu, Doc ...

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