On Mon, 03 Apr 2023 20:55:43 +0200, Bo Berglund via fpc-pascal >On Mon, 3 Apr 2023 14:26:17 -0400, "Jeffrey A. Wormsley via fpc-pascal" ><fpc-pascal@lists.freepascal.org> wrote: > >>I've been using i2c and SPI eeproms for almost two decades. All of them >>can read/write a single byte if that's what you want to do, but the >>write/erase restrictions I noted are there for any parts I've ever used. >>If you write a byte to $00, you cannot write it to $01 without first >>erasing the entire block that it is located in (usually 128 to 256 bytes). >>You can write $FF to $F0, then $F0 to $80, then $80 to $00, as these all >>only involve turning 1 bits into 0 bits, but if you try to write from a $00 >>to a $01, then it will not work, at least not on any part I've ever used, >>as that involves turning a 0 bit into a 1 bit. All of the parts I've >>seen, if you want to modify a single memory location (if the write involves >>turning a 0 bit into a 1 bit), they require you to read the block of data >>into your CPU, modify it there, erase the block, then write the entire >>block data back into the chip. I've seen some parts that have an on-chip >>RAM buffer that would let you read the block into this RAM buffer with one >>command, modify the RAM buffer with a single byte write, erase the block, >>then write the RAM buffer back to the chip, which is a lot faster than >>having to do this yourself with your CPU memory, but it still required the >>block erase and that block erase still counted towards your maximum number >>of erase cycles. I have not seen a chip that allowed completely random >>writes at the byte level before short of a static ram with battery backup. >> >>If you have an i2c part that doesn't work like this, then I would be very >>interested in knowing the part number and seeing a link to the data sheet. >>Such a part would make using these sorts of devices much easier, but to >>date I have never seen one. >> >>Jeff >> >I just tested by writing four 0x00 bytes in a row, then verifying that the >memory read shows these, then writing other data and again verifying that the >data is there. > >All using the i2c-tools commands: > >$ i2ctransfer -y 1 w6@0x50 0x00 0x00 0x00 0x00 0x00 0x00 >$ i2ctransfer -y 1 w2@0x50 0x00 0x00 r8@0x50 >0x00 0x00 0x00 0x00 0xff 0xff 0xff 0xff > >$ i2ctransfer -y 1 w6@0x50 0x00 0x00 0x70 0x30 0x55 0x40 >$ i2ctransfer -y 1 w2@0x50 0x00 0x00 r8@0x50 >0x70 0x30 0x55 0x40 0xff 0xff 0xff 0xff > >The part number is: CAT24C32 by ON Semiconductor (www.onsemi.com) >It is a 128 kbit (16 kbyte) part organized as 64 pages of 256 bytes.
Sorry copied from the wrong datasheet here, should be CAT24C128 -- Bo Berglund Developer in Sweden _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
