AT24C256C-SSHL-T: 256Kb I2C EEPROM for Nonvolatile Data Storage

ElecSuppliers Part Number GuideAug 20, 2026

The AT24C256C-SSHL-T is a 256Kb serial EEPROM from Microchip Technology designed for nonvolatile data storage in electronic systems. It communicates with a host controller through an I2C-compatible two-wire serial interface.

Unlike RAM, EEPROM retains stored information after the system is powered off. This makes the AT24C256C-SSHL-T useful for storing configuration parameters, calibration values, device settings and other data that needs to survive a power cycle.

What Is the AT24C256C-SSHL-T?

The AT24C256C-SSHL-T provides 256Kb of electrically erasable programmable read-only memory, equivalent to 32KB of storage.

The device uses a serial interface rather than a parallel memory bus, allowing it to be connected to a microcontroller with only SDA and SCL communication lines.

The complete AT24C256C-SSHL-T ordering code identifies a particular package and ordering configuration within the AT24C256C family.

This distinction is important when selecting a replacement because different suffixes can represent different package or shipment configurations.

AT24C256C-SSHL-T I2C Interface

The AT24C256C-SSHL-T uses a two-wire I2C-compatible interface.

The serial data line and serial clock line provide communication between the EEPROM and the host controller. Multiple I2C devices can share the same bus when their addresses are configured appropriately.

This makes the EEPROM convenient for embedded systems that already use I2C for sensors, RTC devices or other peripherals.

Compared with a parallel EEPROM, the two-wire interface reduces the number of PCB traces and MCU pins required for communication.

AT24C256C-SSHL-T 256Kb Memory Capacity

The 256Kb capacity provides 32KB of nonvolatile storage.

This is enough for many types of embedded configuration and parameter data.

For example, a controller can use the memory to store calibration constants, user preferences, equipment configuration, serial-related information or production settings.

Because the memory is nonvolatile, these values remain available after the main system loses power.

AT24C256C-SSHL-T Page Write Operation

EEPROM programming is different from ordinary RAM writes.

The AT24C256C family supports page write operations, allowing multiple bytes to be written during a single write cycle within the applicable page boundary.

Page writing can reduce communication overhead when storing structured data.

Firmware should still account for page boundaries and the device's internal write-cycle time. A controller should not assume that the EEPROM is immediately ready for another write simply because the I2C transmission has completed.

AT24C256C-SSHL-T Data Retention

One of the main advantages of EEPROM is that stored information remains available without continuous power.

This makes the AT24C256C-SSHL-T suitable for parameters that must survive system shutdown.

For example, an industrial controller can store calibration information in EEPROM during manufacturing or servicing and retrieve it when the equipment starts again.

The application should distinguish between data that changes occasionally and data that changes continuously. EEPROM is better suited to persistent parameters and relatively infrequent updates than to high-frequency data logging.

AT24C256C-SSHL-T Write Endurance

EEPROM has a finite number of write cycles for each memory location.

For applications that repeatedly update the same address, firmware should avoid unnecessary writes.

A simple strategy is to compare the new value with the existing value and only perform a write when the data has actually changed. More demanding applications can distribute updates across multiple memory locations.

For frequently changing data, a wear-leveling or rotating-storage approach may be appropriate.

AT24C256C-SSHL-T Addressing

The memory architecture uses an internal address system to identify stored data.

The host controller sends the appropriate device and memory addressing information before reading or writing data.

This makes the EEPROM easy to integrate into embedded firmware because the storage can be treated as an addressable nonvolatile memory region.

When several EEPROM devices share the same I2C bus, the available hardware address configuration should be considered to prevent address conflicts.

AT24C256C-SSHL-T Read Operation

Reading data from the EEPROM is performed through the serial I2C interface.

The controller specifies the memory location and then receives the stored data through the SDA line.

Sequential reading can be useful when retrieving larger blocks of configuration data or stored parameters.

For systems that need frequent reads but infrequent writes, the AT24C256C-SSHL-T can provide a simple persistent storage layer without adding an external memory controller.

AT24C256C-SSHL-T Operating Voltage

The AT24C256C family supports low-voltage operation, making it suitable for many modern embedded systems.

The exact supply and electrical characteristics should be checked against the requirements of the target board and host MCU.

I2C pull-up resistors also need to be selected according to the supply voltage, bus capacitance and desired communication speed.

The EEPROM should not be treated as an isolated component because the electrical behavior of the I2C bus depends on the other devices connected to the same lines.

AT24C256C-SSHL-T Applications

The AT24C256C-SSHL-T can be used wherever an embedded system needs small to medium amounts of persistent data storage.

Typical applications include:

Device configuration storage

Calibration parameter storage

User settings

Manufacturing information

Product identification data

Industrial controller parameters

Sensor configuration

These applications generally benefit from EEPROM because the data can be updated electrically while remaining stored when power is removed.

AT24C256C-SSHL-T Hardware Design

The EEPROM should be placed appropriately on the I2C bus and provided with suitable power-supply decoupling.

The SDA and SCL lines require pull-up resistors. Their values depend on bus capacitance, supply voltage and communication speed.

The I2C address pins should also be connected according to the desired device address. If multiple EEPROMs or other I2C peripherals are present, the complete bus address map should be checked during hardware design.

Keeping the I2C traces reasonably short and avoiding unnecessary routing near noisy switching nodes can also improve communication reliability.

AT24C256C-SSHL-T Firmware Considerations

A reliable EEPROM driver should handle write-cycle timing correctly.

After a write operation, the memory may require internal time to complete the programming operation. The host should therefore verify that the device is ready before issuing another write.

Firmware should also avoid unintentionally crossing page boundaries during a page-write operation.

For important configuration data, additional integrity measures such as checksums, version numbers or redundant copies can help detect corrupted or incomplete records.

Choosing the AT24C256C-SSHL-T

The AT24C256C-SSHL-T is a practical choice when an embedded design requires 32KB of nonvolatile storage and a simple I2C interface.

It is well suited to configuration data, calibration values and other parameters that must remain available after the system is powered down.

Before selecting the device, engineers should verify the memory capacity, supply voltage, I2C requirements, write endurance, package configuration and data-update frequency.

For production designs, the complete AT24C256C-SSHL-T Part Number should be maintained in the BOM because the full ordering code identifies the specific component configuration rather than simply referring to the AT24C256C family.