Features
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Low-power, Low-voltage CMOS IDICÒ
Contactless Power Supply, Data Transmission and Programming of EEPROM
Radio Frequency (RF): 100 kHz to 150 kHz, Typically 125 kHz
Automatic Programmable Adaptation of Resonance Frequency
Easy Synchronization with Special Terminators
High-security Method Unilink Challenge Response Authentication by AUT64 Crypto
Algorithm
Encryption Time < 10 ms, Optional < 30 ms Programmable at 125 kHz
320-bit EEPROM Memory in 10 Blocks of 32 Bits Each
Programmable Read/Write Protection
Extensive Protection Against Contactless Malprogramming of the EEPROM
Programming Time for One Block of the EEPROM Typically 16 ms
Main Options Set by EEPROM:
– Bit Rate [Bit/s]: RF/32, RF/64
– Encoding: Manchester, Bi-phase
Description
The e5561 is a member of Atmel’s IDentification IC (IDIC) family for applications
where information has to be transmitted contactlessly. The IDIC is connected to a
tuned LC circuit for power supply and bi-directional data communication (Read/Write)
to a base station. Atmel offers an LC circuit and a chip assembled in the form of a transponder or tag. These units are small, smart and rugged data storage units.
Standard
Read/Write
Crypto
Identification IC
e5561
The e5561 is a Read/Write crypto IC for applications which demand higher security
levels than standard R/W transponder ICs can offer. For that purpose, the e5561 has
an encryption algorithm block which enables a base station to authenticate the transponder. The base station transmits a random number to the e5561. This challenge is
encrypted by both IC and base station. The e5561 sends back the result to the base
station for comparison. As both should possess the same secret key, the results of this
encryption are expected to be equal. Any attempt to fake the base station with a wrong
transponder will be recognized immediately.
The on-chip 320-bit EEPROM (10 blocks of 32 bits each) can be read and written
blockwise by a base station. Two or four blocks contain the ID code and six memory
blocks are used to store the crypto key as well as the read/write options. The crypto
key and the ID code can be protected individually against overwriting. Likewise, the
crypto key cannot be read out.
125 kHz is the typical operational frequency of a system using the e5561. Two read
data rates are programmable. Reading occurs through damping the incoming RF field
with an on-chip load. This damping is detected by the field-generating base station.
Data transmission starts after power-up with the transmission of the ID code and continues as long as the e5561 is powered. Writing is carried out with Atmel's writing
method. To transmit data to the e5561, the base station has to interrupt the RF for a
short time to create a field gap. The information is encoded in the number of clock
cycles between two subsequent gaps.
Rev. 4699A–RFID–04/03
1
Figure 1. Transponder System Example Using e5561
Response
Data
Internal Modes
Coil interface
Challenge
Base
station
Controller
Transponder
Power
Memory
Crypto
e5561
The e5561 can be operated in several internal modes, each providing a special function.
These are:
•
Start-up
•
ID mode
•
Programming mode
•
Direct-access mode
•
Crypto mode
•
Stop mode
•
Password function
The following section gives a short functional description of each mode. A more detailed
description is given in the section "Operating the e5561".
Start-up
After the Power-On Reset (POR) has reset the entire circuit, the e5561 is configured by
reading out the configuration data bits of the EEPROM.
ID Mode
During ID mode, the e5561 transmits an identification data stream (ID code) to the base
station. As the base station reads out data coming from the transponder, this direction of
data transmission will be designated as ’read’.
The ID code is sent in loop as long as the RF field is applied. The single parts of the data
stream and the type of modulation depend on the configuration loaded during start-up.
The following options are available during ID mode:
Programming Mode
2
•
Two different bit rates and modulations
•
Two possible lengths of the ID code (64 bits or 128 bits)
•
Two different terminators
•
A 4-bit preburst followed by terminator 1 between start-up and sending the first data
bits of the ID code
The e5561 must be programmed before being used in a security system. The e5561
contains a 320-bit EEPROM which is arranged in 10 blocks of 32 bits each. Programming the e5561 is carried out blockwise, i.e., every single block has to be programmed
separately. The blocks of the EEPROM are divided into 4 sections:
•
Configuration
•
ID code
•
Crypto key
•
Customer configuration
e5561
4699A–RFID–04/03
e5561
Every section consists of one or more EEPROM blocks. Programming is carried out by
sending the programming data sequence to the e5561. When the base station sends
data to the transponder, this direction of data transmission will be designated as 'write'.
When the base station has sent the data sequence and the specified block has been
programmed, the e5561 transmits the content of the programmed EEPROM block. The
content is always sent in loop with terminator 1. The beginning of the data stream is indicated by a preburst.
During programming, the e5561 monitors several fault and protection mechanisms. If a
fault or a protection violation is detected, the e5561 switches to ID mode.
Direct-access Mode
If the base station transmits a special data sequence to the e5561, it will enter the directaccess mode. The base station can activate two different functions:
•
Read the content of a single block of the EEPROM
In this case, the e5561 transmits the block's content in loop, starting with a preburst
followed by the terminator which is also used to indicate the beginning of the transmission of the specified block data.
•
Reset the e5561 in case of all modes
During direct-access mode, the e5561 monitors several fault and protection mechanisms. If a fault or a protection violation is detected, the e5561 switches to ID mode.
Crypto Mode
In crypto mode, a non-linear high-security encryption algorithm called AUT64 is used to
authenticate the e5561.
After the base station has identified the e5561 (i.e., read the ID code), the base station
may authenticate the transponder by transmitting a challenge. Receiving this data
sequence causes the e5561 to switch to crypto mode.
This initiates the following actions:
•
While calculating the AUT64 result, the transponder transmits the checksum of the
challenge
•
The e5561 generates the response from the calculated result of the AUT64
•
As soon as the calculation is finished, the e5561 interrupts the transmission of the
checksum by sending a terminator
•
The e5561 transmits the response in loop with a terminator back to the base station
The base station can read the response and authentify the transponder. It is possible to
interrupt the calculation of the AUT64 result by sending another data sequence (e.g., if
the checksum was found to be wrong).
During crypto mode, the e5561 monitors several fault and protection mechanisms. If a
fault or a protection violation is detected, the e5561 enters ID mode.
Stop Mode
If two or more transponders are used simultaneously (e.g., in a manufacturing step), it
might be useful to be able to set the transponders to a passive state. To avoid a communication conflict, the base station has to transmit a special data sequence to the active
transponder(s) forcing them to switch to stop mode.
In stop mode, the e5561 switches off the damping as long as the RF field is applied.
After a power-on reset or after having received the software-reset command, the e5561
enters start-up and ID mode again.
During the data sequence of the stop mode, the e5561 monitors fault mechanisms. If a
fault is detected, the e5561 enters ID mode.
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The stop command can be disabled.
Note:
Password Function
For correct stop-mode operation it is necessary that the field be switched off instantly.
The password function is a separate protection mechanism to prevent a base station
from reading or manipulating the internal configuration and data blocks of the e5561
without knowing the password. Only a transition to the crypto mode is possible. If the
password function is active, the base station must first send the password to enable any
other operations.
During password mode, the e5561 monitors several fault and protection mechanism. If a
fault or a protection violation is detected, the e5561 enters ID mode.
Mode Transitions
If the e5561 is in ID mode and the base station transmits a write sequence by interrupting the RF field, the internal mode changes according to the received write sequence. If
an error has been detected or the password function has been enabled, the e5561
remains in ID mode.
A transition to and from all other modes (except the ID mode) is possible by sending the
corresponding write sequence. Once the ID mode is left, switching to another mode is
only possible by sending an uncorrect data sequence to the transponder.
Figure 2. State Diagram of the e5561 (Overview)
Reset
Start-up
ID mode
Gap
Sequence
received
Password
function
Error
Direct-access
mode
Programming
mode
Crypto mode
Transmit data
Transmit data
Transmit data
Stop mode
Gap
Note:
4
This diagram provides only an overview. In reality, more transitions are possible.
e5561
4699A–RFID–04/03
e5561
Building Blocks
Figure 3. Block Diagram
Modulator
Crypto circuit
Coil1
Bitrate
generator
Coil2
CONTROLLER
EEPROM
Memory
Configuration data
Transmission
EEPROM control
Error detection
Encryption
Crypto key
64- or 128-bit code
Test logic
VDD
Analog Front End (AFE)
Controller
VSS
HV Generator
Bit
decoder
Adapt
Analog Front End
Conf. register
Input register
POR
Test pads
The AFE includes all circuits directly connected to the coil. It generates the IC's power
supply and handles the bi-directional data communication with the base station. It consists of the following blocks:
•
Rectifier to generate a DC supply voltage from the AC coil voltage
•
Clock extractor
•
Switchable load between Coil1/Coil2 for data transmission from the IC to the base
station (read)
•
Field gap detector for data transmission from the base station to the IC (write)
The controller has the following functions:
•
Initialize and refresh the EEPROM’s configuration register
•
Control memory access (read, program)
•
Handle correct write data transmission
•
Error detection and error handling
•
Control encryption operation
•
Control the adaptation of resonance frequency
Power-On Reset (POR)
The power-on reset is a delay reset which is triggered when the supply voltage is
applied.
Configuration Register
The configuration register stores the configuration data read out from EEPROM blocks 0
and 9. It is continuously refreshed which increases the reliability of the device (if the initially loaded configuration was wrong or modified, it will be corrected by subsequent
refresh cycles).
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4699A–RFID–04/03
Adapt
The e5561 is able to minimize the tolerance of the resonance frequency between the
base station and the transponder by switching on-chip capacitors in parallel to the LC
circuit of the transponder. By using a coil of approximately 4 mH for a resonance frequency of 125 kHz it is possible to tune the resonance frequency in a range of about
5%. The active value of the adaptation function is carried out automatically every time
the e5561 enters the RF field or when the EEPROM is read out. This depends on a control bit. The automatic adaptation stops when the optimized adaptation has been
reached. This is between 1.0 ms and 5.0 ms (125 kHz) depending on the capacitance
value required. The voltage at Coil 1/Coil 2 after start-up is shown in Figure 8.
Adapt Bits: Details
In addition to the adapt mode, which is executed during the start-up phase by the IC
itself, it is possible to set the adapt bits in the EEPROM manually.
Before carrying out the manual setting of the adapt bits, bit A in block 0 must be set to 1
(see Figure 8).
The content of these 3 bits, that need to be defined, determines the transponder’s
response frequenzy in a limited range.
Bits are set by programming block 0 in the microcontroller.
Bit-rate Generator
The bit-rate generator can deliver bit rates of RF/32 and RF/64 for data transmission
from the e5561 to the base station.
Bit Decoder
The bit decoder forms the signals needed for write operations and decodes the received
data bits in the write data stream.
Modulator
The modulator consists of two data encoders and the terminator generator. There are
two kinds of modulation:
•
•
Manchester
–
Mid-bit rising edge = data H
–
Mid-bit falling edge = data L
Bi-phase
–
Every bit creates a change, a data 0 creates an additional mid-bit change
By using Bi-phase modulation, data transmission always starts with damping on.
HV Generator
The HV generator is a voltage pump which generates about 18 V for programming the
EEPROM.
Memory
The memory of the e5561 is a 320-bit EEPROM which is arranged in 10 blocks of 32
bits each. All 32 bits of a block are programmed simultaneously. The programming voltage is generated on-chip.
Block 0 is reserved for basic configuration data. Blocks 1 to 9 are freely programmable.
Blocks 1 to 4 are used for the ID code, blocks 5 to 8 contain the crypto key. In password
mode, bits 4 to 31 of block 9 contain the password; bits 0 to 3 of block 9 contain the customer-configuration data. If no password is required, the corresponding bits can be
programmed freely.
Note:
6
Data from the memory is transmitted serially, starting with the least significant bit.
e5561
4699A–RFID–04/03
e5561
The basic configuration data in block 0 contains the following information (see Figure 9):
•
Type of modulation and bit rate
•
Length of ID code
•
Several lock-bits
•
Terminator set
The customer-configuration data in block 9 contains (see Figure 10):
•
Lock-bit for ID code (blocks 1 and 4/1 to 4)
•
Lock-bit for crypto key (block 5 to 8)
•
Lock-bit for block 9
•
Password mode enable
Figure 4. Types of Modulation
DataClk
ReadData
0
1
0
1
0
1
0
damping off
Bi-phase
Manchester
damping on
start of transmission
Figure 5. Memory Map
31
Password
0
3
4 bit conf.
Block 9
Crypto key
Blocks 5 to 8
ID code
Blocks 1 to 4
Configuration data
Block 0
32 bits
Crypto Circuit
The crypto circuit uses the certified AUT64 algorithm to encrypt the challenge which is
written to the e5561. The computed result can be read out by the base station. Comparing the encryption results of the base station and the e5561, a high-security
authentification procedure is established. This procedure requires the crypto key of the
e5561 and the base station to be equal. The crypto key is stored in blocks 5 to 8 of the
EEPROM and can be locked by the user to avoid read out or changes.
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4699A–RFID–04/03
Protection
Mechanisms
Several protection mechanisms are implemented into the e5561. These are mainly:
•
Error mechanisms to detect a fault. These mechanisms are always enabled.
•
Programmable protection mechanisms. These mechanisms are optional. When
used, they provide protection against attempts to break the security system.
Password Protection
If the password protection is enabled, the e5561 remains in ID mode even if it has
received a correct write sequence. The only possible operation is to modify the content
of block 9 by sending the correct password bits. In all other cases, an error handling procedure is started and the e5561 enters ID mode.
Lock-bit Protection
A lock-bit is a physical part of the EEPROM's content and is under user control. The
lock-bit protection mechanism has two different effects:
•
Avoid programming (modifying data) of the EEPROM's blocks
•
Avoid reading out the crypto key from the EEPROM using the direct-access mode
If the base station tries to read out the crypto key and the corresponding lock-bit is set,
the e5561 will enter ID mode immediately. Once the crypto key lock-bit is set, the crypto
key can not be modified or read out any more.
There are several lock-bits available, each affecting a special data region of the
EEPROM. The main groups of lock-bits are:
•
Lock-bits to inhibit programming of the specified blocks of the EEPROM
•
Lock-bits to inhibit programming of the specified blocks of a specific address range
In both cases, an attempt to modify a data region protected by a lock-bit will cause an
error handling procedure (i.e., the e5561 enters ID mode)
Stop Mode
The stop mode can also be used as a protection mechanism, e.g., during configuration
at manufacturing. The base station can configure the transponders one by one, forcing
them into stop mode after programming. In this way, transponders can be programmed
even if there are other transponders in the RF field at the same time.
Operating the e5561
General
The basic functions of the e5561 are:
•
Supply the IC from the coil
•
Read data from the EEPROM to the base station
•
Authenticate the IC
•
Receive commands from the base station and program the received data into the
EEPROM.
Several write errors can be detected to protect the memory from being overwritten with
uncorrect data. A password function is implemented ensuring that only authorized people can operate the IC.
Operating modes:
8
•
ID mode: the e5561 sends the ID code to the base station
•
Programming mode: the e5561 programs the EEPROM with data bits received from
the base station
•
Direct-access mode: the e5561 sends the content of single blocks of the EEPROM
to the base station
e5561
4699A–RFID–04/03
e5561
•
Crypto mode: the e5561 computes a response according to the challenge received
from the base station and sends the response to the base station
•
Stop mode: the e5561 stops modulation
An additional password function enables the e5561 to be operated only by a person who
knows the password programmed in the EEPROM memory.
Supply
The e5561 is supplied via a tuned LC circuit which is connected to Coil1 and Coil2 pads.
The incoming RF (actually a magnetic field) induces a current into the coil which powers
the chip. The on-chip rectifier generates the DC supply voltage (VDD, VSS pads). Overvoltage protection prevents the IC from damage due to high field strengths (depending
on the coil, the open-circuit voltage across the LC circuit can reach more than 100 V).
The first occurrence of RF triggers a power-on reset pulse, ensuring a defined start-up
state.
Start-up
The various modes of the e5561 are activated after the first read-out of the configuration. The modulation is on during power-on reset and is off while the configuration is
read. After this initialization period of 128 + POR time FCs, the e5561 starts the automatic adaptation of the resonance frequency. When the adaptation has been carried
out, the e5561 enters ID mode immediately if terminator 2 is selected, otherwise, a data
value of Fh in the selected configuration (modulation, bit rate) is sent followed by the
optionally specified terminator 1 (see Figure 8).
Figure 6. Application Circuit
Coil of base station
Tuned LC
Energy
Coil 1
125 kHz
e5561
VDD
Coil 2
Data
VSS
Figure 7. Voltage at Coil1/Coil2 after Start-up (e.g., RF/32, Manchester, Terminator 1)
Damping off
VCoil1-Coil2
Load config.
(190 FCs)
Automatic
adaptation
Read Fh
Term. 1
Damping on
Read data with selected
modulation and bit-rate
Power-on reset
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4699A–RFID–04/03
Configuration
The configuration data of the e5561 is stored in block 0 of the EEPROM which contains
the following information (see Figure 9):
•
Type of modulation and bit rate
•
ID code length
•
Several lock-bits
•
Selected terminator
•
Stop mode selection for short/long authentication time
•
Adaptation of resonance frequency (if auto-adapt is not used)
The configuration may be changed by programming block 0. However, this is only possible if the lock-bit L_0 in block 0 has not been set.
Figure 8. Configuration Data in Block 0
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
20 bit Supplier Chip ID (SCID)
9
8
7
6
5
L_0 AUT A
S
3
4
2
1
0
1 1 1
adapt bits
MOD
BR
BC
T
S
A
Modulation (0 = Manchester, 1 = Bi-phase)
Bit-rate (0 = RF/32, 1 = RF/64)
Bitcount (0 = 128 bit, 1 = 64 bit) ID
Terminator
Stop mode (0 = off, 1 = on)
Adapt (0 = automatic, 1 = value according to user programmed
adapt bit setting)
AUT
Number of AUT64-times, 0 = 24 times, 1 = 8 times
L_0
Lock-bit for block 0 (1 = active)
adapt bits Tuning bits
T
Test only
Terminator
Terminator
No terminator
BC BR MOD
[1]
[0]
0
1
0
1
0
0
1
1
Block 9 contains the customer configuration and the password (if password function is
enabled). The customer-configuration data in block 9 includes (see Figure 10):
•
Lock-bit for ID code (blocks 1 and 4/1 to 4)
•
Lock-bit for crypro key (block 5 to 8)
•
Lock-bit for block 9
•
Password function enable
If the password function has been enabled, bits 4 to 31 represent the password of the
e5561.
Figure 9. Customer Configuration Data in Block 9
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
28 bit Password
PWD
L_9
L_K
L_ID
10
Password enable ('1' = active)
Lockbit for block 9 ('1' = active)
Lockbit for blocks 5 to 8 (crypto key) ('1' = active)
Lockbit for blocks 1 and 4/1 to 4 (ID code) ('1' = active)
L_9
L_ID
PWD L_K
e5561
4699A–RFID–04/03
e5561
Data Transmission to the Data transmission from the e5561 to the base station is carried out by switching a load
between the coil pads on (damping) and off. This changes the current through the IC coil
Base Station (Read)
which can be detected by the base station.
Figure 10. Signals from the Transponder During Reading
Coil voltage of
the e5560
Coil voltage of
the base station
ID Mode
The ID mode is the default mode after power-up. The ID code is read out of the
EEPROM and sent to the base station.
Modulation and Bit Rate
The different bit rates and modulations of the e5561 can be selected using the appropriate bit in block 0. Available bit rates are RF/32 and RF/64; the e5561 provides Bi-phase
and Manchester modulation.
Figure 11. Types of Modulation
DataClk
ReadData
0
1
0
0
1
1
0
Bi-phase
Manchester
start of transmission
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4699A–RFID–04/03
Data Streams
Reading begins with block 1 (LSB first). Depending on the selected bit count, block 1 is
followed by block 2, 3 and 4 (128-bit bit count) or just by block 4 (64-bit bit count). The ID
code is transmitted in loop or interrupted by the selected terminator, respectively. To
avoid malfunction, the mode register is refreshed continuously with the content of
EEPROM blocks 0 and 9 during reading of block 4. The data streams of the ID mode are
shown in Figure 12.
Figure 12. ID Mode Data Streams
128-bit Bit-count with Terminator
block 1
block 2
block 3
block 4
Terminator
block 1
block 2
block 3
block 4
Terminator
64-bit Bit-count with Terminator
block 1
block 4
Terminator
block 1
block 4
Terminator
128-bit Bit-count without Terminator
block 1
block 2
block 3
block 4
block 1
block 2
block 3
block 4
64-Bit bit-count without Terminator
block 1
Terminators
block 4
block 1
block 4
Terminators are a special pattern to mark the beginning and the end of a code. The terminators may be used to synchronize the base station. They can be detected reliably
since they are a violation of the modulation scheme. After a terminator is sent, transmission of the first bit of the ID code starts with damping on for a certain detection (if
Bi-phase modulation is used).
Note:
Terminator 2 is only available in ID mode; all other modes make use of terminator 1.
Figure 13. Terminators
Terminator 1
Terminator [3-bit period]
bit period
last bit
Terminator 2
Terminator if bitrate = RF/64
[416 FCs]
bit period
last bit 16
64
16
bit period
32
12
first bit
1.5-bit period
(damping = off)
16
128 FCs
208 FCs
(damping = off)
first bit
Terminator if bitrate = RF/32
[384 FCs]
last bit 16
16 16
128 FCs
176 FCs
(damping = off)
first bit
e5561
4699A–RFID–04/03
e5561
Data Transmission to the Data transmission from the base station to the e5561 is carried out by using Atmel’s
write method. It is based on interrupting the RF field with short gaps. The number of field
e5561 (Write)
clock cycles (FC) of two consecutive gaps encodes the 0/1 bit-information to be
transmitted.
Start Gap
The first gap is the start gap which triggers writing. During writing the damping is permanently enabled which simplifies gap detection. The start gap has to be longer than the
subsequent gaps in order to be reliably detected. By default, a start gap will be detected
at any time after start-up intialization has been finished (field-on plus approximately
2 ms).
Figure 14. Signals to the Transponder During Writing
>64 FCs = EOT
RF_Field
1
Start
Gap
0
1
1
0
Field clock
reading
Bit Decoder
reading
writing
The duration of the gaps is usually 50 µs to 150 µs. The time between two gaps is nominally 24 field clocks for a 0 and 56 field clocks for a 1. The bit will be interpreted as 0 if
there are 16 to 32 field clocks since the last field gap; it will be interpreted as 1 if the
number of field clock cycles is in a range of 48 to 64. When there is no gap for more than
64 field clocks, writing is carried out (EOT). If there is a wrong number of field clocks
between two gaps – i.e., one or more data sent were not a valid 0 or 1 – the e5561 will
detect an error (see section “Error handling”).
Figure 15. Bit Decoding Scheme (Number of FCs Between Two Consecutive Gaps)
16
1
32
48
64
Bit decoder
fail
OPcodes
0
fail
1
EOT
The OPcode is defined as the first two bits of a writing sequence. It is used for changing
the operational modes of the e5561. There are three valid OPcodes: The programming
mode and direct-access mode are entered with the 10 OP code, 01 is used to initiate the
authentication of the e5561, and the OPcode '00' disables modulation until a POR
occurs.
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4699A–RFID–04/03
Figure 16. OP Codes
Programming mode
Direct-access mode
10
1
0
more data...
Start gap
Crypto mode
01
0
Stop mode
11
1
Programming Mode
more data...
1
1
> 64 clocks
Programming the EEPROM of the e5561 is carried out blockwise, i.e., every single
block has to be programmed separately. The programming-mode write sequence is
shown in Figure 17. After OPcode 10, the 32 data bits have to be sent followed by the
four address bits specifiying the block to be programmed (each LSB first). The
sequence is completed by sending an EOT (end of transmission), i.e., more than 64
field clocks without any gap.
Figure 17. Programming Mode Write Sequence
OP code
10 0
data bits
Data bits
block address
31 0 ADR 3
EOT
0 . . . . . .9
When the entire write sequence has been written to the e5561, programming may proceed. There is a 64-clock delay between the end of writing and the start of
programming. During this time, the EEPROM's programming voltage VPP is measured
and the lock-bit for the block to be programmed is examined. Further, VPP is continually
monitored throughout the programming cycle. If VPP is too low, the chip starts error handling. The programming time is 16 ms (including erase) with a field clock frequency of
125 kHz.
Figure 18. Programming
EOT received
Write mode
programming ends
16 ms
Check VPP
0.512 ms
programming starts
VPP on
Operation
14
write
VPP and lock ok?
erase EEPROM
program EEPROM
read
e5561
4699A–RFID–04/03
e5561
After programming has been carried out, the e5561 sends an Fh preburst followed by
terminator 1. After that, the data just programmed is read out of the EEPROM and sent
in loop with terminator 1. This enables the base station to detect a malprogramming by
comparing the data transmitted with the data read out after programming. This mode
remains until a POR occurs or another gap is detected.
Figure 19. Programming Mode Data Stream
write sequence
program block
read Fh
Terminator 1
read block
Terminator 1
read block
Figure 20. Coil Voltage in Programming Mode
V Coil1-Coil2
End of programming
sequence
Direct-access Mode
16 ms
programming
read Fh
Term.
read block
Term.
read block
The direct-access mode is typically used to read out the content of a single block of the
EEPROM. The write sequence is shown in Figure 21. Following the OPcode 10, the
address of the block to be read has to be sent (LSB first).
Figure 21. Direct-access Mode Write Sequence
10 0
ADR
3
EOT
It is always possible to read the content of block 0 and the four blocks of the ID code.
The blocks containing the crypto-key (blocks 5 to 8) can only be accessed when the corresponding lock-bit in block 9 is not set. Therefore, there is no possibility for a nonauthorized person to read out or modify the crypto key if it is locked. Figure 23 shows
the direct-access-mode data stream. After the write sequence, an FFh preburst is sent
followed by terminator 1. After that, the addressed block and terminator 1 are sent in
loop.
Figure 22. Direct-access Mode Data stream
write sequence
read FFh
Terminator 1
read block
Terminator 1
read block
15
4699A–RFID–04/03
Figure 23. Coil Voltage in Direct-access Mode
VCoil1-Coil2
End of direct access
sequence
Software Reset
read FFh
Term.
read block
Term.
read block
To set up the ICs in a defined state, a software reset command can be executed by
sending a pseudo block address Fh. The write sequence is shown in Figure 25. The
Reset command is also accepted during stop mode.
Figure 24. Software Reset
10
Crypto Mode
1
1
1
1
EOT
The crypto mode enables a high-security authentication of the e5561. For this purpose,
a certified algorithm called AUT64 is used. The crypto-mode write sequence is shown in
Figure 25. After the OPcode 01, the challenge is sent to the e5561 (LSB first).
Figure 25. Crypto Mode Write Sequence
01 0
Challenge bits
63
EOT
After the write sequence, the AUT64-algorithm is started. The computation of the
response takes about 30/10 ms (125 kHz). During this time, a checksum – the number
of the challenge bits set to 1 – can be read by the base station. Once the response has
been computed, the base station can read the response in loop with the terminator 1.
This remains until a POR occurs or another gap is detected. The data stream of the
crypto mode is shown in Figure 26.
Figure 26. Crypto Mode Datastream
write sequence
read FFh
read 00b
checksum Terminator 1
response
Terminator 1
During the encryption calculation, the checksum is sent in loop with a special pattern
(see Figure 28). The bits of the checksum are sent with LSB first. If the base station
detects an error by comparing the checksum, the calculation of the response can be
interrupted by sending a new challenge. This will start the authentication procedure
again.
16
e5561
4699A–RFID–04/03
e5561
Figure 27. Checksum
Data FFh
Data
6-bit checksum
0
1
1
1
1
1
1
1
1
0
Data FFh
Data
5
0
1
1
1
1
1
1
1
1
0
0
Figure 28. Coil Voltage in Crypto Mode
V
Response calculated
Coil1-Coil2
End of programming
sequence
read FFh
read
00b
checksum
read
FFh
Term.
response
Term.
The encryption time is programmable in two options: The entire algorithm AUT64 is executed 8 or 24 times. This feature can be set at block 0, bit 7.
Stop Mode
If several transponders enter the RF field of the base station one after the other (e.g., in
a manufactoring step), it might be useful to be able to set the transponder in a passive
state. In this case, the transponder may be collected one by one and disabled after
being read out. To avoid a communication conflict, the base station has to transmit a
special data sequence to the active transponder(s) forcing them to enter the stop mode.
During stop mode, the e5561 switches off the damping as long as the RF field is
applied. After a power-on reset, the e5561 enters the start-up and the ID mode again.
An other possibility to exit the stop mode is to send the software reset (see Figure 30).
This command results in a new initialization of the IC.
Figure 29. Stop Mode Data Sequence
11
EOT
Figure 30. Write Sequence to Disable Password Function
10
XXXX
4
Password
31 1 0 0 1
EOT
X = do not care (both 0 or 1 acceptable)
Password Function
The password function is a separate protection mechanism to prevent that a base station from reading or manipulating the internal configuration and data blocks of the e5561
without knowing the password.
The password function may be used to prevent unauthorized programming or reading
via direct-access mode. If the password bit in block 9 of the EEPROM is set, only certain
operations are posible, i.e., reading the ID code in ID mode or authentication.
17
4699A–RFID–04/03
For programming or direct-access mode, the password function has to be disabled by
receiving the password.
If this function is enabled, the customer configuration can only be changed by an authorized person using the correct password of the e5561.
During password mode, the e5561 monitors several fault and protection mechanism. If a
fault or a protection violation is detected, the e5561 enters ID mode.
Error Handling
Several error conditions can be detected to ensure that only valid operations affect the
e5561.
Errors while Writing Data There are four detectable errors possible during writing data to the e5561:
•
Field gap was not detected
•
Wrong number of field clocks between two gaps, e.g., 37 FCs
•
The OPcode is not valid (11)
•
The number of bits received is incorrect; valid bit counts are:
–
programming mode: 38 bits
–
direct-access mode: 6 bits
–
crypto mode: 66 bits
–
stop mode: 2 bits
If any of these four conditions is detected, the e5561 stops writing and enters ID mode.
This can easily be analyzed using the damping which is usually on during writing. It
changes according to the selected modulation scheme in ID mode.
Errors During Programming
Mode
If the writing sequence has been transmitted successfully, there are three errors that
may prevent the e5561 from programming the data to the EEPROM:
•
The programming voltage VPP is too low, i.e., the field strength is not high enough
•
The lock-bit of the adressed block is set
•
The password function is enabled
In these cases, the procedure stops immediately after the error has been detected and
the IC reverts to ID mode.
Errors During Direct-access
Mode
In addition to the possible errors mentioned before, two errors may occur in directaccess mode:
•
The lock-bit of the addressed block 5 to 8 is set
•
The password function is enabled
In these cases, the IC enters ID mode after the end of the writing sequence.
Errors During Crypto Mode
In crypto mode, ONE error mechanism is active, that may prevent the e5561 from sending the correct response:
•
Error during the crypto writing sequence
The e5561 will enter ID mode immediately if an error in the writing sequence is detected.
If the password function is enabled, the e5561 enters ID mode after having completed
the writing sequence.
18
e5561
4699A–RFID–04/03
e5561
Error Handling During
Password Mode
If password function is enabled and the password transmitted does not match the programmed password, the full programming sequence is performed but without
programming block 9. This makes it more difficult to find out the correct password by
trial and error because in each case the result of the operation can only be recognized
after the whole sequence has been processed. This increases the time needed to check
a certain number of combinations.
Figure 31. Simplified Error Handling of the e5561
Power-on reset
Start-up
Send ID code
Receive OPcode
fail
ok
Receive data
fail
EOT
Password
function
Password ok
or disabled
Number of bits
fail
fail
Error handling
ok
Lock-bit
fail
ok
VPP
fail
ok
fail
Program
19
4699A–RFID–04/03
Authentication
Especially for applications with high-security demands such as immobilizer systems, the
e5561 contains an optimized authentication procedure with the following advantages:
•
Secure and fast authentication (< 100 ms)
•
Application-optimized high-security algorithm
•
Customer-specific generation of unique keys
Therefore, a high-security data transmission and encryption as well as a short authentication time is achieved.
For further information, some additional documentation and programs are available:
•
The encryption process of the e5561
•
Key generating program
•
Algorithm program
Figure 32. Authentication Procedure
Base station
e5561
Generate RF field
Receive the ID code and
select the crypto key
ID code
Transmit ID code
Challenge
Receive the datastream
Generation of random number R
Calculation of the challenge R'
(encrypted random number R)
Transmit the challenge
Decryption of R' to R
Receive the checksum
Checksum in loop
Transmit the checksum
AUT64 with R as input value
AUT64 with R as input value
Calculate the valid response
Calculation of the response
Interrupt transmission of
checksum
Receive the response
generated by the e5561
Response in loop
Transmit response
Authenticate by comparing
the responses of e5561
to its own result
20
e5561
4699A–RFID–04/03
e5561
Initialization
Before using the e5561 in crypto mode, it has to be initialized.
First, the crypto key to be used by the crypto algorithm has to be generated by the keygenerating program. This program guarantees that each crypto key is unique, no other
e5561 has the same key. This key has to be stored in the memory (block 5 - block 8) of
the e5561 via the programming mode. Once the crypto key is locked, it can not be overwritten or read out anymore with direct-access mode.
For correct authentication it is necessary that base station and transponder both use the
same key. Therefore, the base station needs to know which transponder is currently in
the field. Only then, the base station can select the key corresponding to this particular
transponder. For this identification the e5561 sends a string of data after it has been
powered up. This ID code must also be stored in the e5561.
Starting the Authentication
After power-up the various modes (bit rate, encoding) are read out of block 0. Then, the
e5561 transmits the ID code to identify itself. Thereby, the base station can identify the
transponder and knows which crypto key to use. The base station forces the e5561 into
crypto mode by sending the OPcode 01 followed by a 64-bit string, the challenge.
Challenge
The base station generates a 64-bit random number R. This number is the starting value
of the actual encryption algorithm. To improve security, this random number is not sent
directly to the transponder, but is encrypted by means of a part of the crypto key. The
encoded result R' is then transmitted as challenge to the transponder. Once the transponder has received the encoded random number R', it recovers the random number R
originally generated by the base station. Both devices, the base station as well as the
transponder, then start with the encryption of this number. If the number of received bits
is incorrect, the e5561 leaves the crypto mode and enters read mode immediatly, transmitting the ID code.
Checksum
For verification of the received challenge, the e5561 sends a checksum (representing
the number of 1 of the challenge) with a special pattern in loop until the encryption is finished (less than 10 ms - optionally 30 ms).
Encryption
For encryption, the optimized high-security algorithm AUT64 is used. The elementary
parts of this 64-bit block cipher are transposition and substitution (Figure 34). For more
detailed information on this algorithm additional documentation is provided. The entire
algorithm AUT64 is executed 24 times. At each of these 8/24 times, another key is generated out of the crypto key. Therefore, the algorithm keeps changing and a highsecurity level is achieved. This is confirmed by statistical analysis.
For more detailed information, the description 'The Encryption Process of the e5561'
can be provided.
Response
The 64-bit result of the algorithm is reduced to 32 bits using logical operations. This 32bit response is sent back to the base station for comparison. If the correct keys were
used, the result generated inside the base station is identical to the result sent by the
e5561. The response is transmitted in loop including the terminator until the IC is powered by the RF field. This gives the base station enough time to check the validation of
the response.
21
4699A–RFID–04/03
Figure 33. Atmels' Crypto Algorithm AUT64
a0
a1
a2
a3
a4
a5
a6
a7
a6
a7
Input of AUT64 in round n
Byte permutation s
a0
a1
a2
a3
a4
a5
Function f
Substitution t
Bit permutation s
Substitution t
a0
22
a1
a2
a3
a4
a5
a6
a7
Input of AUT64 in round n+1
e5561
4699A–RFID–04/03
e5561
Figure 34. Authentication Example
Power-on reset
5 ms
Read ID code
20 ms
Start-up
ID mode
(if 64 bit ID used, <10 ms possible)
Send challenge
30 ms
ID mode
Challenge
Checksum
and Encrypt
ENCRYPTION
(AUT64)
and Checksum
Response
< 10 ms (8 times of AUT64)
30 ms option (24 times of AUT64)
10 ms
Checksum
and Encrypt
Response
t < 65 ms (8 times of AUT64 and reduced ID used)
t < 75 ms (8 times of AUT64)
t < 95 ms (24 times AUT64)
23
4699A–RFID–04/03
Absolute Maximum Ratings
All voltage are given corresponding to VSS.
Parameters
Symbol
Value
Unit
Supply voltage
VDD
-0.3 to +7.0
V
Input voltage
VIN
VSS -0.3 £ VIN £ VDD +0.3
V
IC1/C2
10
mA
Power dissipation (dice)
Ptot
100
mW
Current into Coil1/Coil2
(1)
Operating temperature range
Tamb
-40 to +85
°C
Storage temperature range(2)
Tstg
-40 to +125
°C
Assembly temperature (t £ 5 min)
Tass
170
°C
Notes:
1. Free-air condition. Time of application: 1 s.
2. Data retention reduced.
Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device.
Operating Range
Tamb = 25°C; reference terminal is VSS; DC operating voltage VDD - VSS = 2 V (unless otherwise noted).
Parameters
Test Conditions
RF frequency range
Supply current
Clamp voltage
Typ.
Max.
Unit
100
125
150
kHz
IDD
15
µA
fRF = 125 kHz, programming
IDD
100
µA
No clock
IDD
100
250
500
nA
Current into Coil1/Coil2 = 5 mA
Vcl
7.5
9.0
10.2
V
C1,2
Programming voltage
Data retention
Min.
fRF
fRF = 125 kHz, read and write
Equivalent coil input capacitance
(without self-adapt)
Programming time
Symbol
VPP
fRF = 125 kHz
30
15
tPP
16
16
pF
19
V
ms
tretention
10
Years
Programming cycles
ncycle
100,000
–
Lowest operating voltage for
programming
Vmfs
1.8
V
24
e5561
4699A–RFID–04/03
e5561
Figure 35. Application Example
from
oscillator
125 kHz
4.2 mH
4.2 mH 386 pF
Energy
Coil 1
e5561
Coil 2
Data
to base
station
fres =
386 pF
1
2p
LC
= 125 kHz
Ordering Information
Extended Type Number
Package
e5561A-DOW
Remarks
DOW
–
Pads
Note:
Name
Pad Window
Function
Coil1
136 ´ 136 m
1st coil pad
Coil2
136 ´ 136 m
2nd coil pad
VDD
78 ´ 78 m2
Positive supply voltage
VSS
82 ´ 82 m
Negative supply voltage (GND)
2
2
2
For normal (coil-driven) operation, the e5561 needs only Coil1 and Coil2.
Chip Dimensions
Test pads
e5561
Coil2
VDD
1600 mm
Coil1
VSS
4930 mm
25
4699A–RFID–04/03
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© Atmel Corporation 2003.
Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company’s standard warranty
which is detailed in Atmel’s Terms and Conditions located on the Company’s web site. The Company assumes no responsibility for any errors
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Printed on recycled paper.
4699A–RFID–04/03
xM