The Microchip Technology Inc 47C16 EERAM is a 16Kbit SRAM with EEPROM Backup. The I2C EERAM Memory is a Low-Cost NVSRAM that Eliminates the Need for an External Battery to Retain Data. The device is organized as 2048 x 8 bits and utilizes the I2C serial interface. The 47C16 provides infinite read and write cycles to the SRAM while the EEPROM cells provide high endurance non-volatile storage of Data. With an external capacitor, SRAM data is automatically transferred to the EEPROM upon power-loss. Data can also be transferred manually by using either the hardware store pin or by software control. Upon power-up, the EEPROM data is automatically recalled to the SRAM. Recall can also be initiated through software control. The unlimited endurance makes the EERAM useful in applications that need to constantly monitor or record data.
Power failures are inevitable. When power returns, your program restarts, but with the contents of all of the variables lost. Often times, it would be advantageous to have critical values saved and made available when power returns. EERAM makes it easy to do just that. In this article, we will explore the use of EERAM and build a simple demonstration project that will automatically save a program variable when power fails and then restore it when power returns.