ATMEL E5561

Features
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Low-power, Low-voltage CMOS IDIC®
Contactless Power Supply, Data Transmission and Programming of EEPROM
Radio Frequency (RF): 100 kHz to 150 kHz, Typically 125 kHz
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
1. Description
Standard
Read/Write
Crypto
Identification IC
e5561
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.
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.
4699D–RFID–09/06
Transponder System Example Using e5561
Transponder
Challenge
Base
station
Response
Coil interface
Power
Data
Controller
Figure 1-1.
Memory
Crypto
e5561
2. Internal Modes
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” on page 10.
2.1
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.
2.2
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:
• 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
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e5561
2.3
Programming Mode
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
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.
2.4
Direct-access Mode
If the base station transmits a special data sequence to the e5561, it will enter the direct-access
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.
2.5
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
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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.
2.6
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.
The stop command can be disabled.
Note:
2.7
For correct stop-mode operation it is necessary that the field be switched off instantly.
Password Function
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.
2.8
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 incorrect data sequence to the transponder.
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e5561
Figure 2-1.
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:
This diagram provides only an overview. In reality, more transitions are possible.
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3. Building Blocks
Figure 3-1.
Block Diagram
Modulator
Crypto Circuit
Bitrate
Generator
Coil2
Conf. Register
CONTROLLER
Configuration Data
Transmission
EEPROM Control
Error Detection
Encryption
3.1
VSS
Crypto Key
64- or 128-bit Code
Test Logic
VDD
EEPROM
Memory
HV Generator
Adapt
Analog Front End
Bit
Decoder
Coil1
Input Register
POR
Test pads
Analog Front End (AFE)
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)
3.2
Controller
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
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e5561
3.3
Power-On Reset (POR)
The power-on reset is a delay reset which is triggered when the supply voltage is applied.
3.4
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).
3.5
Adapt
The derivation of the resonant frequency between the base station and transponder can be minimized by switching the on-chip capacitors in parallel to the LC circuit of the transponder.
By using an antenna coil in the range of 4 mH matched to 128 kHz, a tuning range of about 5%
can be achieved by the internal switch capacitors.
For the adapt bit setting, the related bits (9 to 11) and the activation bit (6) in the configuration
block 0 have to be set. The typical resonant frequency range is determined with 128 kHz using
the 000 setting and 121 kHz using the 111 setting.
Note:
3.6
Due to a mailfunction, adapt bit setting 111 should not be used.
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.
3.7
Bit Decoder
The bit decoder forms the signals needed for write operations and decodes the received data
bits in the write data stream.
3.8
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.
3.9
HV Generator
The HV generator is a voltage pump which generates about 18 V for programming the
EEPROM.
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3.10
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:
Data from the memory is transmitted serially, starting with the least significant bit.
The basic configuration data in block 0 contains the following information (see Figure 5-4 on
page 12):
• 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 5-5 on page 12):
• 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 3-2.
Types of Modulation
DataClk
ReadData
0
1
0
0
1
1
0
damping off
Bi-phase
Manchester
damping on
start of transmission
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e5561
Figure 3-3.
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
3.11
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.
4. 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.
4.1
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.
4.2
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.
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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)
4.3
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.
5. Operating the e5561
5.1
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 incorrect
data. A password function is implemented ensuring that only authorized people can operate the
IC.
Operating modes:
• 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
• 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.
5.2
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.
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e5561
5.3
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 190 + POR time FCs, the e5561 activates the adaption bit setting defined by
configuration and enters in ID mode. If the IC is configured with terminator 1, a data value of FH
acc. selected data coding is sent in advance of terminator and read data (see Figure 5-2).
Figure 5-1.
Application Circuit
Coil of base station
Tuned LC
Energy
Coil 1
125 kHz
e5561
VDD
Coil 2
Data
Figure 5-2.
VSS
Voltage at Coil1/Coil2 after Start-up (e.g., RF/32, Manchester, Terminator 1)
Damping off
VCoil1-Coil2
Load config.
(190 FCs)
Power-on reset
5.4
Read Fh
Term. 1
Damping on
Read data with selected
modulation and bit-rate
Adaptation setting
Configuration
The configuration data of the e5561 is stored in block 0 of the EEPROM which contains the following information (see Figure 5-3 on page 12):
• 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
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.
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Figure 5-3.
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
AUT
L_0
adapt bits
7
6
5
3
4
2
1
0
1 1 1
adapt bits
MOD
BR
BC
T
S
A
8
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 (1 = value according to user programmed
adapt bit setting)
Number of AUT64-times, 0 = 24 times, 1 = 8 times
Lock-bit for block 0 (1 = active)
Tuning bits
L_0 AUT A
T
S
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 5-5):
• 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 5-4.
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
5.5
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
Data Transmission to the Base Station (Read)
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 which can be
detected by the base station.
Figure 5-5.
Signals from the Transponder During Reading
Coil voltage of
the e5560
Coil voltage of
the base station
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e5561
5.5.1
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.
5.5.2
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 5-6.
Types of Modulation
DataClk
1
0
ReadData
0
0
1
1
0
damping off
Bi-phase
Manchester
damping on
start of transmission
5.5.3
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 5-7.
Figure 5-7.
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
block 4
block 1
block 4
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5.5.4
Terminators
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:
Figure 5-8.
Terminator 2 is only available in ID mode; all other modes make use of terminator 1.
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
5.6
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
Data Transmission to the e5561 (Write)
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 clock cycles
(FC) of two consecutive gaps encodes the 0/1 bit-information to be transmitted.
5.6.1
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 initialization has been finished (field-on plus approximately 2 ms).
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e5561
Figure 5-9.
Signals to the Transponder During Writing
>64 FCs = EOT
RF_Field
Start
Gap
1
0
1
1
0
Field clock
reading
5.6.2
reading
writing
Bit Decoder
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” on page 19).
Figure 5-10. Bit Decoding Scheme (Number of FCs Between Two Consecutive Gaps)
16
1
32
48
64
Bit decoder
fail
5.6.3
0
fail
1
EOT
OPcodes
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 OPcode, 01 is used to initiate the authentication of
the e5561, and the OPcode '00' disables modulation until a POR occurs.
Figure 5-11. OPcodes
Programming mode
Direct-access mode
10
1
0
more data...
Start gap
Crypto mode
01
Stop mode
11
0
more data...
1
1
1
> 64 clocks
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5.6.4
Programming Mode
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 5-12.
After OPcode 10, the 32 data bits have to be sent followed by the four address bits specifying
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 5-12. Programming Mode Write Sequence
OP code
10 0
block address
31 0 ADR 3
EOT
0 . . . . . .9
data bits
Data bits
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 5-13. Programming
EOT received
Write mode
programming ends
16 ms
Check VPP
0.512 ms
programming starts
VPP on
Operation
write
VPP and lock ok?
erase EEPROM
program EEPROM
read
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 5-14. Programming Mode Data Stream
write sequence
16
program block
read Fh
Terminator 1
read block
Terminator 1
read block
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e5561
Figure 5-15. Coil Voltage in Programming Mode
V Coil1-Coil2
End of programming
sequence
5.6.5
16 ms
programming
read Fh
Term.
read block
Term.
read block
Direct-access Mode
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 5-16. Following the OPcode 10, the address
of the block to be read has to be sent (LSB first).
Figure 5-16. 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 non-authorized person to read out or
modify the crypto key if it is locked. Figure 5-18 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 5-17. Direct-access Mode Data Stream
write sequence
read FFh
Terminator 1
read block
Terminator 1
read block
Figure 5-18. Coil Voltage in Direct-access Mode
VCoil1-Coil2
End of direct access
sequence
5.6.6
read FFh
Term.
read block
Term.
read block
Software Reset
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 5-20 on page 18. The Reset
command is also accepted during stop mode.
Figure 5-19. Software Reset
10
1
1
1
1
EOT
17
4699D–RFID–09/06
5.6.7
Crypto Mode
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 5-20.
After the OPcode 01, the challenge is sent to the e5561 (LSB first).
Figure 5-20. 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 5-21.
Figure 5-21. Crypto Mode Datastream
write sequence
read 00b
read FFh
checksum Terminator 1
response
Terminator 1
During the encryption calculation, the checksum is sent in loop with a special pattern (see Figure
5-23). 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.
Figure 5-22. 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 5-23. 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.
18
e5561
4699D–RFID–09/06
e5561
5.6.8
Stop Mode
If several transponders enter the RF field of the base station one after the other (e.g., in a manufacturing 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 5-25). This
command results in a new initialization of the IC.
Figure 5-24. Stop Mode Data Sequence
11
EOT
Figure 5-25. 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)
5.6.9
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 possible, i.e., reading the ID code in ID mode or authentication.
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.
5.7
Error Handling
Several error conditions can be detected to ensure that only valid operations affect the e5561.
19
4699D–RFID–09/06
5.8
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.
5.8.1
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 addressed 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.
5.8.2
Errors During Direct-access Mode
In addition to the possible errors mentioned before, two errors may occur in direct-access 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.
5.8.3
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.
20
e5561
4699D–RFID–09/06
e5561
5.8.4
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 5-26. 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
21
4699D–RFID–09/06
5.9
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 under NDA:
• The encryption process of the e5561
• Key generating program
• Algorithm program
Figure 5-27. 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
22
e5561
4699D–RFID–09/06
e5561
5.9.1
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 key-generating 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.
5.9.2
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.
5.9.3
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 immediately, transmitting the ID code.
5.9.4
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 to optionally 30 ms).
5.9.5
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 5-29). 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 high-security level is achieved. This is confirmed
by statistical analysis.
For more detailed information, the description 'The Encryption Process of the e5561' can be provided under NDA.
23
4699D–RFID–09/06
5.9.6
Response
The 64-bit result of the algorithm is reduced to 32 bits using logical operations. This 32-bit
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.
Figure 5-28. Atmel’s Crypto Algorithm AUT64
a0
a1
a2
a3
a4
a5
a6
a7
a6
a7
Input of AUT64 in round n
Byte permutation σ
a0
a1
a2
a3
a4
a5
Function f
Substitution τ
Bit permutation σ
Substitution τ
a0
24
a1
a2
a3
a4
a5
a6
a7
Input of AUT64 in round n+1
e5561
4699D–RFID–09/06
e5561
Figure 5-29. 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
ENCRYPTION
Checksum
and Encrypt
(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)
25
4699D–RFID–09/06
6. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
All voltages 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
Ptot
100
mW
Operating temperature range
Tamb
–40 to +85
°C
(2)
Storage temperature range
Tstg
–40 to +125
°C
Assembly temperature (t ≤ 5 min)
Notes: 1. Free-air condition. Time of application: 1 s.
Tass
170
°C
Current into Coil1/Coil2
Power dissipation (dice)(1)
2. Data retention reduced.
7. Operating Range
Tamb = 25°C; reference terminal is VSS; DC operating voltage VDD – VSS = 2 V (unless otherwise noted).
Parameters
Test Conditions
Symbol
Min.
Typ.
Max.
Unit
fRF
100
125
150
kHz
RF frequency range
Supply current
Clamp voltage
fRF = 125 kHz, read and write
IDD
15
µA
fRF = 125 kHz, programming
IDD
100
µA
No clock
IDD
100
250
500
nA
Vcl
7.5
9.0
10.2
V
Current into Coil1/Coil2 = 5 mA
Equivalent coil input capacitance
(without self-adapt)
C1,2
Programming voltage
Programming time
30
VPP
fRF = 125 kHz
15
pF
16
tPP
19
16
V
ms
tretention
10
Years
Programming cycles
ncycle
100,000
–
Lowest operating voltage for
programming
Vmfs
1.8
V
Data retention
Figure 7-1.
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
26
1
2p
= 125 kHz
LC
e5561
4699D–RFID–09/06
e5561
8. Ordering Information
Extended Type Number
Package
e5561A-DOW
DOW
Remarks
–
9. Pads
Note:
Name
Pad Window
Function
Coil1
136 × 136 m
1st coil pad
Coil2
136 × 136 m2
2nd coil pad
VDD
78 × 78 m
2
Positive supply voltage
VSS
82 × 82 m
2
Negative supply voltage (GND)
2
For normal (coil-driven) operation, the e5561 needs only Coil1 and Coil2.
10. Chip Dimensions
Test pads
e5561
Coil2
VDD
1600 µm
Coil1
VSS
4930 µm
11. Revision History
Please note that the following page numbers referred to in this section refer to the specific revision
mentioned, not to this document.
Revision No.
History
4699D-RFID-09/06
•
•
•
•
4699C-RFID-08/05
• Last page: Disclaimer text changed
4699B-RFID-03/05
• Put datasheet in a new template
• Section 5.9 “Authentication” on page 22 changed
• Section 5.9.5 “Encryption” on page 23 changed
Put datasheet in a new template
Features on page 1 changed
Section 3.5 “Adapt” on page 7 changed
Figure 5-2 “Voltage at Coil1/Coil2 after Start-up (e.g., RF/32, Manchester,
Terminator 1) on page 11 changed
• Section 5.4 “Configuration” on page 11 changed
• Figure 5-3 “Configuration Data in Block 0” on page 12 changed
27
4699D–RFID–09/06
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4699D–RFID–09/06