Capture and store critical information without constant power with 48LM01 and STM32F091RC

EERAM 2 Click is based on the 48LM01, a 1024-Kbit SRAM with EEPROM backup in each memory cell from Microchip. The user can treat this device as a full symmetrical read/write SRAM with no limits on cell usage. The device handles backup to EEPROM on any power disruption, so the user can effectively view this device as an SRAM that never loses its data. The SRAM is organized as 131,072 x 8 bits with access via the SPI serial interface. The backup EEPROM is invisible and cannot be accessed by the user independently. The 48LM01 includes circuitry that detects VCC dropping below a certain threshold, shuts its connection to the outside environment, and transfers all SRAM data to the EEPROM portion of each cell for safekeeping. When VCC returns, the circuitry automatically returns the data to the SRAM, and the user’s interaction with the SRAM can continue with the same data set. When power is first

applied to the click board™, the VCAP capacitor is charged to VCC through the 48LM01 IC. During normal SRAM operation, the capacitor remains charged, and the device monitors the level of system VCC. If the system VCC drops below a set threshold, the device interprets this as a power-off or brown-out event. The device suspends all I/O operation, shuts off its connection with the VCC pin, and uses the saved energy in the capacitor to power the device through the VCAP pin as it transfers all SRAM data to EEPROM. On the next power-up of VCC, the data is transferred back to SRAM, the capacitor is recharged, and the SRAM operation continues. Besides standard 4-wire SPI lines, 48LM01 has an additional HOLD pin. This pin can be used for transmission suspension to the 48LM01 while in the middle of a serial sequence without retransmitting the entire sequence. It must be held high any time this function is not

being used. Once the device is selected and a serial sequence is underway, the HOLD pin may be pulled low to pause further serial communication without resetting the serial sequence. The 48LM01 is internally organized as a continuous SRAM array for reading and writing, along with a non-volatile EEPROM array that is not directly accessible to the user but can be refreshed or recalled on power cycles or software commands. The SRAM array is continuously addressable, so the entire array can be written without accessing pages. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin

headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is

provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.