PCA24S08

The PCA24S08 provides 8192 bits of serial electrically erasable and programmable Read-only memory (EEPROM) organized as 1024 words of 8 bits each. Data bytes are received and transmitted via the serial I2C-bus. Access permissions limiting reads or writes are set via the I2C-bus to isolate blocks of memory from improper access.

The PCA24S08 is intended to be pin compatible with standard 24C08 serial EEPROM devices except for pins 1, 2, and 3, which are address pins of PCA24S08 in the standard part. Other exceptions to the PCA24C08 serial EEPROM datasheet are noted the "Serial EEPROM Exception" section later in this document. All bits are sent to or read from the device, most significant bit first, in a manner consistent with the 24C08 serial EEPROM. The bit fields in this document are correspondingly listed with the MSB on the left and the LSB on the right.

The EEPROM memory is broken up into 8 blocks of 1 k bits (128 bytes) each. Within each block, the memory of PCA24S08 is physically organized in to 8 pages of 128 bits (16 bytes) each. In addition to these 8 k bits, there are two more 128-bit pages that are used to store the access protection and ID information. There are a total of 8448 bits of EEPROM memory available in the PCA24S08. Access protection (both read and write) is organized on a block basis for blocks 1 through 7 and on a page and a block basis for block 0. Protection information for these blocks and pages is stored in one of the additional pages of EEPROM memory that is addressed separately from the main data storage array. See "Access Protection" for more details.

The ID value (see "ID Configuration") PCA24S08 is located in the ID page of the EEPROM, the second of the additional 16 byte pages. Writes from the serial interface may include from one to 16 bytes at a time, depending on the protocol followed by the bus master. All page accesses must be properly aligned to the internal EEPROM page.

The EEPROM memory offers an endurance of 100,000 write cycles per byte, with 10 year data retention. Writes to the EEPROM take less than 5 ms to complete. After manufacturing, all EEPROM bits will be set to a value of '1'.