I2C EEPROMs are very popular in embedded system as they provides very good solution for storing data on a non-volatile storage device. AT24xxx series serial eeprom works on I2C protocol. This tutorial will help you understand in depth detail of i2c EEPROMs so you can easily use EEPROMs in your projects.
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Atmel (www.atmel.com),Catalyst (www.catsemi.com),Fairchild (www.fairchildsemi.com),Microchip (www.microchip.com),Philips (www.semiconductor.philips.com),Rohm (www.rohm.com),ST (www.st.com),Xicor (www.xicor.com),and others. DescriptionThis is a simple EEPROM module meant to enable reading the first 256 bytesof an EEPROM (on a SDRAM DIMM for example).
However, it will access serialEEPROMs on any I2C adapter. The supported devices are generically called24Cxx, and are listed above; however the numbering for theseindustry-standard devices may vary by manufacturer.This module was a programming exercise to get used to the new projectorganization laid out by Frodo, but it should be at least completelyeffective for decoding the contents of EEPROMs on DIMMs.DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants.The other devices will not be found on a DIMM because they respond to morethan one address.DDC Monitors may contain any device.
Often a 24C01, which responds to all 8addresses, is found.Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn’t get thespecification, so it is guess work and far from being complete.The Microchip 24AA52/24LCS52, ST M34C02, and others support an additionalsoftware write protect register at 0x30 - 0x37 (0x20 less than the memorylocation). The chip responds to “write quick” detection at this address butdoes not respond to byte reads. If this register is present, the lower 128bytes of the memory array are not write protected. Any byte data write tothis address will write protect the memory array permanently, and thedevice will no longer respond at the 0x30-37 address. The eeprom driverdoes not support this register. Lacking functionality.
Full support for larger devices (24C04, 24C08, 24C16). These are nottypically found on a PC. These devices will appear as separate devices atmultiple addresses. Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).These devices require two-byte address fields and are not supported. Enable Writing. Again, no technical reason why not, but making it easyto change the contents of the EEPROMs (on DIMMs anyway) also makes it easyto disable the DIMMs (potentially preventing the computer from booting)until the values are restored somehow.
Simple example, how to read and write EEPROM 24C01 via I2C with Arduino Uno.
EEPROM
If you do not know, what EEPROM is, see wikipedia page.For more info about used EEPROM AT24C01A, see attached datasheet.
![]() I2C
Inter-Integrated Circuit is serial synchronous bus. It uses two wires and Arduino Uno has this interface at analog pins A4 and A5. Library for I2C in Arduino is called Wire. More info at wikipedia page.
Code
Code for Arduino is based on code from page Using Arduino with an I2C EEPROM, with some differences:
Code at playground use AT24C256 EEPROM with 256kbit. This EEPROM use 2bits for memory addressing, but AT24C01 use only one bit.
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