product information
contact memory tags
Features
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2, 4, 8, 16, 32 or 64 k bytes of non-
volatile EEPROM
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Rugged construction to military
standards
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Asynchronous UART/RS232
compatible
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Unique 32 bit serial number
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Secure 64 bit password
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Selective memory write protection
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16 bit CRC error correction
asynchronous serial data compatible
with common integrated circuit
UARTs (universal asynchronous
receiver transmitter) operating in
'simplex' bi-directional mode at
57.6k bits per second.
Unique serial number
Each e-tag has a unique 32 bit serial
number stored in ROM which
cannot be altered or erased but can
be read by a host device.
Secure password protection
e-tag contact memory has a true
password protection function
whereby a 64 bit password can be
set and stored securely in EEPROM.
If enabled, the password must be
supplied, for each tag, to access the
data. Prior to a password being set
a host device can access full
read/write functionality. Once a
password has been set on an e-tag
the host must provide a matching
password before further reading or
writing of EEPROM is permitted. A
previously set password can be
cleared by supplying a matching
existing password.
Memory write protection
Areas of EEPROM can be
permanently locked preventing
further writing of data but allowing
continued reading of the data from
this area. This can be used to lock
just a few bytes of EEPROM or the
whole e-tag. Once a lock has been
set it cannot be reversed. A lock
can be extended allowing data to be
protected as it is added.
Error correction
All host communications to and from
an e-tag contain a 16 bit cyclic
redundancy check (CRC) stored
within the communication packet.
For command messages sent by
the host controller, the host must
calculate the CRC value. On receipt
of the command packet the e-tag
will perform its own CRC calculation
and compare it to the contents of
the received packet CRC value. If
the two do not match then an error
code will be returned by the e-tag.
Conversely, for response messages
the e-tag calculates the CRC and
places it in the response packet. On
receipt of the response packet the
host should perform its own CRC
calculation and compare it to the
contents of the received packet
CRC. If the two do not match then it
is the responsibility of the host to
take appropriate action.
A detailed interface specification is
available to integrators on request.
Oxley e-tags are contact memory
tags containing up-to 64 k bytes of
EEPROM non-volatile memory
housed in small rugged metal cans.
e-tags are intended for permanent
attachment to host assets in order
store any kind of digital information
relevant to the asset, creating a
secure portable micro-database co-
resident with the asset itself.
When interfaced to a host controller
an e-tag is capable of having its
memory read-from or written-to
virtually an unlimited number of
times. When disconnected from a
host controller the data stored can
be retained for over 100 years. e-
tags are passive containing no
battery or internal power source to
retain data.
Physical protocol
Physical signalling between e-tag
and a host controller uses
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