AT24RF08C datasheet(2/21 Pages) ATMEL

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AT24RF08C

General Overview

The AT24RF08C is intended to be pin compatible with

standard serial EEPROM devices except for pins 1, 2 and

3, which are address pins in the standard part. Other

exceptions to the AT24C08 Serial EEPROM data sheet are

noted in the “Serial EEPROM Exceptions” section later in

this document. Connection of an external coil antenna and

optional tuning capacitor, normally via a two conductor

wire, is all that is required to complete the RFID hardware

requirements.

Throughout this document, the term “reader” is defined as

the base station that communicates with the chip. Under all

expected conditions, it actually serves as both a reader and

writer. The term ‘tag’ is used to indicate the chip when

operating as an RFID transponder with the coil attached.

All bits are sent to or read from the device, most significant

bit first, in a manner consistent with the AT24C08 Serial

EEPR O M . The bit fi elds in th is do cumen t a r e

correspondingly listed with the MSB on the left and the LSB

on the right.

EEPROM Organization

The EEPROM memory is broken up into 8 blocks of 1K

bits (128 bytes) each. Within each block, the memory is

physically organized into 8 pages of 128 bits (16 bytes)

each. In some instances, accesses take place on a 32-bit

(4 byte) word basis. In addition to these 8K 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 on the AT24RF08C.

Access protection (both read and write) is organized on a

block basis for blocks 1 through 7 and on a page and 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” on page

3 for more details.

The ID value (see “ID Configuration” on page 7) is located

in the ID page of the EEPROM, the second of the additional

16 byte pages.

Writes from the serial port may include from one to 16

bytes at a time, depending on the protocol followed by the

bus master. Accesses to the EEPROM from the RFID port

are on either a word (32 bits) or page (128 bits) basis only.

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 and tamper bit take less than 10 ms to

complete.

Completion time for writes initiated from the RFID port are

different depending on the situation. When external power

is supplied to the chip through the VCC pin, writes to the

EEPROM and tamper bit take less than 11.8 ms when

measured from the last modulation edge before the write to

the first after the write. When powered from the coil pins at

125 KHz, the EEPROM write time will be 5.8 ms and the

tamper write time will be 7.9 ms.

After manufacturing, all EEPROM bits except in the device

revision byte (see “Access Protection” page 5) will be set to

a value of 1 and the tamper bit will be set to 0.

Device Access

The third device address bit in the two wire protocol that is

usually matched to A

2 (pin 3) on a standard AT24C08 serial

EEPR OM is int e rn ally conn ect ed hig h , so d e vice

addresses A8 through AF (hex) are used to access the

memory on the chip. The general command encoding used

by the serial port for EEPROM accesses is shown below in

Device Access Examples, where B

2-0 is the block number,

2-0 is the page number within the block and A3-0 is the byte

address within the page. Bits denoted as “x” are ignored by

the device.

The PROT pin is used as a power good signal. When this

pin is low, the serial port is held in reset and all sticky bits

are set to one. When high, activity on the serial bus is

permitted.

Device Access Examples

For Write Operations:

1 0 1 0 1 B

2 B1 0B0 P2 P1 P0 A3 A2 A1 A0

7 D6 D5 D4 D3 D2 D1 D0

…

For Read Operations:

1 0 1 0 1 X X 1

7 D6 D5 D4 D3 D2 D1 D0

…

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