AT24RF08-EK Atmel, AT24RF08-EK Datasheet - Page 3

• Manufacturer Part Number: AT24RF08-EK
• Description: KIT EVAL FOR AT24RF08CN-10SC
• Manufacturer: Atmel
• Type: Dual Access EEPROMr

Specifications of AT24RF08-EK

• Contents: Atmel Asset ID Kit CDROM, 4 RFID Tags, Reader with Serial Port Cable and 9V Power Supply
• For Use With/related Products: AT24RF08C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Access Protection
All access protection bits are stored on a separate page of
the EEPROM that is not accessed using the normal
commands of an AT24C08 memory. See the “Access
Protection Page” section on page 5, for more detail on this
information.
The RFID Access (RF) fields in the Access Protection Page
determines whether or not the corresponding block within
the memory can be read or written via the RFID interface. If
an illegal command is attempted, the command will be
aborted. The MSB, if clear, prohibits all accesses from the
RFID port, and the LSB if clear prohibits writes from the
RFID port. The fields are stored in the EEPROM and
organized as follows:
RFID Access Fields (RF)
The Protection Bits (PB) fields in the Access Protection
Page determine what type of accesses will be permitted via
the serial port for each of the blocks on the chip. If an illegal
access is attempted, the command will be NACK’ed. The
MSB, if clear, prohibits all accesses to the block, and the
LSB if clear prohibits writes. The fields are stored in the
EEPROM and are organized as follows:
Protection Bits (PB)
The Tamper Write (TW) bits within the access protection
page control whether or not a write will be permitted into
the corresponding block of memory when the Tamper Bit is
set. If the Tamper Bit is a 1 and the TW bit is a 0, then
writes to that block from the RFID port are not permitted. In
all other cases, writes are permitted according to the RF
field value for that block. The value of this bit does not affect
accesses from the serial port.
MSB
MSB
0
0
1
1
0
0
1
1
LSB
LSB
0
1
0
1
0
1
0
1
Function
No accesses permitted from RFID port
No accesses permitted from RFID port
Reads only from the RFID port
No restrictions for RFID accesses
Function
No accesses permitted in the block
No accesses permitted in the block
Read only, writes cause a NACK
Read/write - No access constraints for
data within this block
Accessed within the Access Protection Page is an
individual CMOS Sticky Bit (SB) for each of the 8 blocks on
the device. When the value of the sticky bit is 0, the
Protection Bits (PB) for the corresponding block may not be
changed via the software. These bits are all set to one
when power is initially applied or when the PROT pin is low.
These sticky bits may be written only to a 0 via the serial
interface using the standard serial write operations.
Reading the sticky bits does not affect their state.
Because access permissions are set individually for each
of the blocks, all reads via the serial port will only read
bytes within the block that was specified when the current
addres s was latched into the device (with a wr ite
command). The block address bits (B
with the write command are ignored on a read command.
After the read of the last byte within a block, the internal
serial address wraps around to point at the beginning of
that block. After the write of the last byte in a page, the
internal address is wrapped around to point to the
beginning of that page. If more than 16 bytes are sent to
the device with a write command, the data written to any
overlapping bytes will be corrupted.
If the WP pin is high, all write operations are prohibited
from the serial port, although write commands may be used
to set the address for a subsequent read command.
Block 0 Write Protection Bits
The AT24RF08C provides a mechanism to divide block 0
into eight 128-bit (16 byte) pages that can be individually
protected against writes from either port. These eight write
protection (WP) bits are stored within a byte of the access
protection page and are organized such that the LSB
protects the first 128 bits and so on. If a bit in this byte is set
to a one and the PB
permitted on the page corresponding to the WP bit. If the
WP bit is set to a 0 or the PB
then writes are not permitted in that page.
The Write Protection hierarchy for serial accesses is shown
on the following page. In this drawing the bits within the
boxes to the left of the arrows are the only thing that
determine whether or not the bit in the box to the right of
the arrow can be written. Read access control is not shown
in this diagram. Addresses listed in this diagram are for the
serial port assuming that the R/W bit in the command byte
is set to 0.
0
field is set to 11, then writes are
AT24RF08C
0
is any value other than 11,
2
or B
1
) that are sent
3