3.3.3 Serial EEPROM with Unique MAC Address

The SAM9X60-Curiosity board embeds one Microchip 24AA025E48 serial EEPROM. The 24AA025E48 features 2048 bits of serial Electrically-Erasable Programmable Read-Only Memory (EEPROM) organized as 256 words of eight bits each and is accessed via an I2C-compatible (2-wire) serial interface. In addition, the 24AA025E48 incorporates an easy and inexpensive method to obtain a globally unique MAC or EUI address (EUI-48™). For more information about the 24AA025E48, refer to the product web page.

The EUI-48 addresses can be assigned as the actual physical address of a system hardware device or node, or it can be assigned to a software instance. These addresses are factory-programmed by Microchip and unique. They are permanently write-protected in an extended memory block located outside the standard 2-Kbit memory array.

Figure 3-11. EEPROM 24AA025E48
Table 3-3. EEPROM PIO Signal Descriptions
PIO Signal Name Shared PIO Signal Description
PA0 EEPROM_TWD_PA0 TWI and SPI TWI data
PA1 EEPROM_TWCK_PA1 TWI and SPI TWI clock

In the SAM9X60-Curiosity usage context, the EEPROM device is used as a “software label” to store board information such as chip type, manufacturer name and production date, using the last two 16-byte blocks in memory. The information contained in these blocks should not be modified.