AT24C256 EEPROM Features, Functions, Working Principle, Applications and AT24C256 vs 24LC256
14 December 2023
Ⅰ. What is programmable read-only memory?
Ⅱ. Overview of AT24C256 EEPROM
Ⅲ. Pin configuration of AT24C256 EEPROM
Ⅳ. What are the features of AT24C256 EEPROM?
Ⅴ. Functions of AT24C256 EEPROM
Ⅵ. Working principle of AT24C256 EEPROM
Ⅶ. Block diagram of AT24C256 EEPROM
Ⅷ. What are the applications of AT24C256 EEPROM?
Ⅸ. What are the differences between AT24C256 and 24LC256?
Programmable read-only memory (PROM or FPROM) is a computer storage memory chip. It can write data into the device by using hardware called a PROM programmer. After the PROM is programmed, it can only hold that data and it cannot be programmed anymore. This kind of memory is often used in products that can translate languages, such as video game consoles or electronic dictionaries, as their permanent storage solution.
AT24C256 is a 256kbit serial electrically erasable programmable read-only memory produced by ATMEL. It can store large amounts of data without external power supply and additional circuitry. In addition, it can connect 4 pieces of this IC in parallel on a 2-wire bus, which is especially suitable for data acquisition systems with high-capacity data storage requirements. The capacity of AT24C256 is 256Kbit and the data transmission speed is 400kHz. It can store a variety of data types including binary numbers, ASCII characters, etc. The device adopts an 8-pin double-row in-line package and has the advantages of compact structure and large storage capacity.
Replacements and equivalents:
• AT24C512
• 24AA256
• 24LC512
• 24LC1026
• 25LC040
As shown in the picture, AT24C256 has eight pins. Its pin names and descriptions are as follows.
Pin 1 (A0): Address input
Pin 2 (A1): Address input
Pin 3 (A2): Address input
Pin 4 (GND): Ground
Pin 5 (SDA): Serial data
Pin 6 (SCL): Serial clock
Pin 7 (WP): Write protect
Pin 8 (VCC): Power supply
• It adopts 8-pin double row in-line package and has compact structure.
• AT24C256 requires minimal current supply for read and write operations.
• AT24C256 is small in size and suitable for various occasions.
• It can rewrite the stored data multiple times.
• AT24C256 has a storage capacity of 256Kb and can be used to store large amounts of data.
1. Read and write function: At the rising edge of each pulse of SCL, we write data to E²PROM. On every falling edge of SCL pulse, we read data from E²PROM. Data changes on SDA are only valid when SCL is low.
2. Start signal: When SCL is high level, the data on SDA will change from high level to low level and serve as a start signal. All operating commands to the AT24C256 must be issued after the start signal.
3. End signal: When SCL is high, the data on SDA will change from low level to high level, and this will be used as the end signal. Any operation command of AT24C256 must end after the end signal.
4. Response signal: All data and address information are serially input and output through the SDA line. Whenever the AT24C256 receives a byte of data, it sends a low level signal as a response to the received data.
1. Clock and data transfer
Under normal circumstances, SDA will be pulled high by an external device. The data on SDA will only change when SCL is low. When SCL is high, changes in SDA indicate a change in status.
2. START
When SCL is high, SDA changes from high to low to indicate the start of data transfer. This status must precede all commands.
3. End state (STOP)
When SCL is high, SDA changes from low to high to indicate the end of data transfer.
4. Response status (ACK)
All addresses and data are transferred to the memory serially in 8-bit form. The memory sends a zero signal to SDA in the 9th clock cycle to indicate that 8-bit data has been received.
• Configuration information storage: AT24C256 can store various configuration information such as passwords to prevent the risk of data leakage.
• Automotive electronics: In automotive electronic systems, it can be used to store information such as vehicle parameters, fault codes, etc., thereby improving the reliability and safety of the vehicle.
• Data storage: The AT24C256 facilitates data storage in embedded systems or IoT devices, enabling it to perform read and write operations even in the absence of a network connection.
• Program running status storage: AT24C256 can be used to store the program running status so that the program running status can be restored when the power is cut off and restarted, thereby improving the stability of the program running.
• Medical equipment: In medical devices, it serves to guarantee both the proper functioning of the equipment and the well-being of patients.
• IoT devices: Due to the characteristics of data and configuration information storage, AT24C256 is very suitable for application in IoT devices to achieve remote monitoring and management.
The AT24C256 and 24LC256 are both 256K-bit I2C interface EEPROMs with a capacity of 32K bytes and an 8-bit width. Each device supports independent reading and writing of 32 bytes per page. The AT24C256 operates at frequencies up to 400KHz, while the 24LC256 operates at a faster speed of 1MHz. The primary distinction lies in their maximum speeds, with the 24LC256 exhibiting a significantly improved speed compared to the AT24C256.
Frequently Asked Questions
1. What is EEPROM used for?
EEPROM is a type of non-volatile ROM that enables individual bytes of data to be erased and reprogrammed. That is why EEPROM chips are known as byte erasable chips. EEPROM is usually used to store small amounts of data in computing and other electronic devices.
2. How big is the memory in AT24C256?
The AT24C256 I2C Interface EEPROM Memory Module is based on EEPROM chips of AT24C series, 256K bit capacity, that's 32k bytes. The EEPROM module communicates with Arduino through the I2C interface.
3. What is the write cycle of AT24C256?
The Write Cycle Time of 5 ms only applies to the AT24C128/256 devices bearing the process letter “B” on the package (the mark is located in the lower right corner on the top side of the package).
4. How many bytes are in a page of the AT24C256?
The AT24C256 has a page size of 64 bytes. This means that up to 64 bytes of data can be written or read in a single I2C transaction.
