LICAL-ENC-HS001 [ETC]
HS SERIES ENCODER DATA GUIDE; HS系列编码器数据手册
| 型号： | LICAL-ENC-HS001 |
| 厂家： | 
ETC |
| 描述： | HS SERIES ENCODER DATA GUIDE |
| 文件： | 总9页 (文件大小：392K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
HIGH SECURITY
HS SERIES
ENCODER
WIRELESS MADE SIMPLE ®
HS SERIES ENCODER DATA GUIDE
®
DESCRIPTION
CipherLinx
Technology
EVALUATED
HS Series encoders and decoders are
designed for maximum security remote
control applications. The HS encoder
encodes the status of up to eight buttons or
contacts into a highly secure encrypted
output intended for wireless transmission
via a RF or infrared link. The HS Series
uses CipherLinx™ technology, which is
based on the Skipjack algorithm developed
by the U.S. National Security Agency
(NSA) and has been independently
evaluated by ISE. CipherLinx™ never
sends or accepts the same data twice,
never loses sync, and changes codes on
every packet, not just every button press.
In addition to state-of-the-art security, the
tiny 20-pin SSOP packaged parts also
offer innovative features, including up to 8
data lines, multiple baud rates, individual
“button level” permissions, keypad user
PIN, encoder identity output, low power
consumption, and easy setup.
0.309
(7.85)
0.207 (5.25)
0.026
(0.65)
0.284
(7.20)
0.013
(0.32)
0.007
(0.18)
0.030
(0.75)
Figure 1: Package Dimensions
FEATURES
APPLICATIONS INCLUDE
CipherLinx™ security technology
ISE evaluated
Keyless Entry / Access Control
Door and Gate Openers
Never sends the same packet twice Security Systems
Never loses sync
PIN-protected encoder access
8 selectable data lines
“Button level” permissions
Encoder ID available at decoder
Wide 2.0 to 5.5V operating voltage
Low supply current (370µA @ 3V)
Ultra-low 0.1µA sleep current
Selectable baud rates
Remote Device Control
Car Alarms / Starters
Home / Industrial Automation
Remote Status Monitoring
ORDERING INFORMATION
PART #
DESCRIPTION
LICAL-ENC-HS001
LICAL-DEC-HS001
MDEV-LICAL-HS
HS Encoder
HS Decoder
No programmer required
HS Master Development System
Small SMD package
Patents Pending
HS encoders are shipped on reels of 1,600
Revised 1/28/08
ELECTRICAL SPECIFICATIONS
RECOMMENDED PAD LAYOUT
HS Series encoders and decoders are implemented in an industry standard
20-pin Shrink Small Outline Package (20-SSOP). The recommended layout
dimensions are shown below.
Parameter
Designation
Min.
Typical
Max.
Units
Notes
POWER SUPPLY
Operating Voltage
Supply Current:
At 2.0V VCC
VCC
ICC
2.0
–
5.5
VDC
–
0.047
(1.19)
–
–
–
240
370
670
300
470
780
µA
µA
µA
1
1
1
At 3.0V VCC
At 5.0V VCC
0.016
(0.41)
Power-Down Current:
At 2.0V VCC
IPDN
–
–
–
0.10
0.10
0.20
0.80
0.85
0.95
µA
µA
µA
–
–
–
At 3.0V VCC
At 5.0V VCC
ENCODER SECTION
Input Low
VIL
VIH
VOL
VOH
–
0.0
–
–
0.15 x VCC
V
V
2
3
–
–
–
–
–
0.026
(0.65)
Input High
0.8 x VCC
VCC
0.6
–
Output Low
–
–
V
Output High
VCC - 0.7
–
V
Output Sink Current
Output Drive Current
SEND High to DATA_OUT
ENVIRONMENTAL
Operating Temperature Range
–
–
–
–
25
25
–
mA
mA
mS
0.234 (5.94)
0.328 (8.33)
–
–
–
3.3
–
-40
–
+125
°C
–
Figure 2: HS Series Encoder PCB Layout Dimensions
Table 1: Electrical Specifications
PRODUCTION CONSIDERATIONS
Notes
These surface-mount components are designed to comply with standard reflow
production methods. The recommended reflow profile is shown below and
should not be exceeded, as permanent damage to the part may result.
1. Current consumption with no active loads.
2. For 3V supply, (0.15 x 3.0) = 0.45V max.
3. For 3V supply, (0.8 x 3.0) = 2.4V min.
Lead-Free
Sn / Pb
275
ABSOLUTE MAXIMUM RATINGS
260°C Max
250
240°C Max
225
Supply Voltage VCC
-0.3
to
+6.5
VDC
200
Any Input or Output Pin
-0.3
to VCC + 0.3 VDC
Max. Current Sourced By Output Pins
Max. Current Sunk By Output Pins
Max. Current Into VCC
Max. Current Out Of GND
Operating Temperature
25
mA
mA
mA
mA
°C
175
150
25
250
300
to
125
100
75
-40
-65
+125
+150
Storage Temperature
to
°C
50
*NOTE* Exceeding any of the limits of this section may lead to permanent
damage to the device. Furthermore, extended operation at these maximum
ratings may reduce the life of this device.
25
0
0
20
40
60
80
100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420
TIME (SECONDS)
Figure 3: HS Series Reflow Profile
Baud Rate
Decoder Activation Time
*CAUTION*
4,800
67
36
This product is a static-sensitive component. Always wear an ESD
28,800
wrist strap and observe proper ESD handling procedures when
working with this device. Failure to observe this precaution may
result in device damage or failure.
Table 2: Encoder SEND to Decoder Activation Times (mS)
Page 3
Page 2
PIN ASSIGNMENTS
PIN DESCRIPTIONS
Data Lines
1
2
3
4
5
6
7
8
9
20
19
18
17
16
15
14
13
12
11
The encoder has eight data lines, D0 through D7. when the SEND line goes high,
the states of these lines are recorded, encrypted for transmission, then
reproduced on the outputs of the decoder.
SEL_BAUD
SEL_BAUD Baud Rate (bps)
This line is used to select the baud
rate of the serial data stream. The
state of the line allows the selection of
one of two possible baud rates, as
shown in the adjacent table.
0
1
4,800
28,800
10
Table 5: Baud Rate Selection Table
The baud rate must be set before power-up. The encoder will not recognize any
change in the baud rate setting after it is on.
Figure 4: HS Series Encoder Pin Assignments
SEL_TIMER
Pin Name
D0-D7
Pin Number
1, 2, 13, 14, 17-20
I/O
I
I
I
Description
Data Input Lines
This line is used to set the length of inactive time before PIN reentry is required.
GND
SEL_BAUD
SEL_TIMER
GND
3
4
Baud Rate Selection Line
PIN Time-Out Timer Select Line
Ground
These lines are connected to ground.
KEY_IN
5, 6
7
—
I
KEY_IN
Key Input Pin
This line is used to input the key from the decoder.
TX_CNTL
DATA_OUT
MODE_IND
CREATE_PIN
SEND
8
External Transmitter Control Line
Serial Data Output
O
O
O
I
I
—
TX_CNTL
9
This line goes high when the SEND line goes high and low when the SEND line
goes low. This can be used to power up external devices, such as a transmitter,
when the encoder is sending data, and power it down when the encoder is
asleep. It can also be used to drive a LED for visual indication of transmission.
10
11
12
15, 16
Mode Indicator Output
Create PIN Mode Selection Line
Encoder Send Data Line
Positive Power Supply
DATA_OUT
VCC
The encoder will output an encrypted serial data stream on this line. This line can
directly interface with all Linx RF transmitter modules or it can be used to
modulate an IR diode.
Table 3: HS Series Encoder Pin Assignments
NOTE:
None of the input lines have internal pull-up or pull-down resistors. The input lines must always be in a
known state (either GND or VCC) at all times or the operation may not be predictable. The designer must
ensure that the input lines are never floating, either by using external resistors, by tying the lines directly to
GND or VCC, or by use of other circuits to control the line state.
MODE_IND
This line will be activated while the encoder is in Get Key Mode or Create Pin
Mode. It allows the connection of a LED or other indicator for user feedback.
CREATE_PIN
ENCODER MODE_IND INDICATION TABLE
When this line is taken high, the encoder will enter Create PIN Mode and allow
the user to set a Personal Identification Number (PIN) to control encoder access.
The MODE_IND line is the primary means of indicating the state of the encoder
to the user. The table below provides definitions for the MODE_IND signals.
SEND
Get Key Mode
ON for 1 second after a successful key transfer.
When this line goes high, the encoder will record the states of the data lines,
encrypt them for transmission, and send the packet as a serial bit stream through
the DATA_OUT line at the baud rate selected by the state of the SEL_BAUD line.
Flashes* for 15 seconds while waiting for user to enter a PIN. It
Create PIN Mode stops flashing when the fourth number is entered or when it
times out.
VCC
Enter PIN Mode
ON when each PIN is entered.
This is the positive power supply.
*Flash = ON for 200ms and OFF for 200ms
Table 4: HS Series Encoder MODE_IND Definitions
Page 4
Page 5
REMOTE CONTROL OVERVIEW
HS SERIES OVERVIEW
Wireless remote control is growing in popularity and finding its way into more
unique applications. Remote Keyless Entry (RKE) systems for unlocking cars or
opening garage doors quickly come to mind, but how about a trash container that
signals the maintenance office when it needs to be emptied? The idea behind
remote control is simple: a button press or contact closure on one end causes
some action to be taken at the other. Implementation of the wireless RF stage
has traditionally been complicated, but with the advent of simpler discrete
solutions and modular products, such as those from Linx, implementation has
become significantly easier.
The HS Series encoder encrypts the status of up to eight buttons or contacts into
highly secure encrypted serial data stream intended for wireless transmission via
an RF or infrared link. The series uses CipherLinx™ technology, which is based
on the Skipjack algorithm developed by the United States National Security
Agency (NSA). The CipherLinx™ protocol in the HS Series has been
independently evaluated by Independent Security Evaluators (ISE). A full
evaluation white paper is available at www.linxtechnologies.com/cipherlinx.
The encoder combines eight bits representing the state of the eight data lines
with counter bits and integrity bits to form a 128-bit message. To prevent
unauthorized access, this message is encrypted with CipherLinx™ in a mode of
operation that provides data integrity as well as secrecy. CipherLinx™ never
sends or accepts the same data twice, never loses sync, and changes codes
with every packet, not just every button press.
Encoder and decoder ICs are
generally employed to maintain the
security and uniqueness of a wireless
RF or IR link. These devices encode
the status of inputs, usually button or
contact closures, into a data stream
suitable for wireless transmission.
Upon successful recovery and
validation, the decoder’s outputs are
set to replicate the states of the
encoder’s inputs. These outputs can
then be used to control the circuitry
required by the application.
VCC
Tx
LR
ENC
HS
Series
Decoding of the received data signal is accomplished by a corresponding Linx
HS Series decoder. When the decoder receives a valid command from an
encoder, it will activate its logic-level outputs, which can be used to control
external circuitry. The encoder will send data continuously as long as the SEND
line is held high. Each time the algorithm is executed, the counter is
decremented, causing the code to be changed with the transmission of each
packet. This, combined with the large counter value and the timing associated
with the protocol, ensures that the same transmission is never sent twice.
Series
DEC
Rx
LR
GND
HS
Series
Series
Figure 5: Remote Control Block Diagram
An 80-bit key used to encrypt the data is created in the decoder by the user. The
decoder is placed into Create Key Mode, and a line is toggled 10 times, usually
by a button. This is required to gather entropy to ensure that the key is random
and chosen from all 280 possible keys. A high-speed timer is triggered by each
rise and fall of voltage, recording the time that the line is high and low. The 80-
bit key is generated by combining the low-order bits of the twenty timer values.
To create an association, the key, a 40-bit counter, and a decoder-generated ID
are sent to the encoder via a wire, contacts, IR, or other secure serial connection.
Prior to the arrival of the Linx HS Series, encoders and decoders typically fell into
one of two categories. First were older generation, low-security devices that
transmitted a fixed address code, usually set manually with a DIP switch. These
products were easy to use, but had significant security vulnerabilities. Since they
sent the same code in every transmission, they were subject to code grabbing.
This is where an attacker records the transmission from an authorized
transmitter and then replays the transmission to gain access to the system.
Since the same code is transmitted every time, the decoder has no way to
validate the transmission.
The HS Series allows the end user or manufacturer to create associations
between the encoder and decoder. If the encoder and decoder have been
associated through a successful key exchange, then the decoder will respond to
the encoder’s commands based on its permissions. If an encoder has not been
associated with a decoder, its commands will not be recognized.
These concerns resulted in the development of a second type of encoder and
decoder that focused on security and utilized a changing code to guard against
code grabbing. Typically, the contents of each transmission changes based on
complex mathematical algorithms to prevent someone from reusing a
transmission. These devices gained rapid popularity due to their security and the
elimination of manual switches; however, they imposed some limitations of their
own. Such devices typically offer a limited number of inputs, the transmitter and
receiver can become desynchronized, and creating relationships and
associations among groups of transmitters and receivers is difficult.
The user or manufacturer may also set “button level” permissions. Permission
settings control how the decoder will respond to the reception of a valid
command, either allowing the activation of an individual data line or not. The
decoder is programmed with the permission settings during set-up, and those
permissions are retained in the decoder’s non-volatile memory.
The HS decoder has the ability to identify and output a decoder-assigned
identification number for a specific encoder. An encoder’s key, a 40-bit counter,
and permissions are stored in one of fifteen memory locations within the
decoder. The decoder is able to output an 8-bit binary number that corresponds
to the memory location of the encoder’s information. This provides the ability to
identify the specific encoder from which a signal originated. This identification
can be used in various ways, including systems that record access attempts or
in applications where the originating user needs to be known.
The HS Series offers the best of all worlds. The HS Series uses an advanced
high security encryption algorithm called CipherLinx™ that will never become
desynchronized or send the same packet twice. It is easily configured without
production programming and allows for “button level” permissions and unique
encoder and decoder relationships. Eight inputs are available, allowing a large
number of buttons or contacts to be connected.
To learn more about different encoder and decoder methodologies, please refer
to Application Note AN-00310.
Page 6
Page 7
HS SERIES SECURITY OVERVIEW
HS SERIES SECURITY OVERVIEW (CONT.)
Encryption algorithms are complex mathematical equations that use a number,
called a key, to encrypt data before transmission. This is done so that
unauthorized persons who may intercept the transmission cannot access the
data. In order to decrypt the transmission, the decoder must use the same key
that was used to encrypt it. The decoder will perform the same calculations as
the encoder and, if the key is the same, the data will be recovered.
Another factor is how often the message will be repeated and the intervals
between repeats. Some applications use a counter to change the appearance of
the message. This is good, but at some point, the counter will roll over and the
message will be repeated. For example, if attackers were to copy an encrypted
message and save it, they could potentially gain access to the protected device
at a later time. Depending on the size of the counter, this vulnerability could
occur frequently. The HS Series uses a 40-bit decrementing counter to keep this
from ever happening. If the SEND line was held high continuously at the high
baud rate (28,800bps), it would take 889 years before the counter would reach
zero, at which point the key would be erased and the encoder would have to get
a new key. The math used is: [(240 * 25.5ms) / (1000mS*60s*60m*24h*365d)] =
889 years. This large counter prevents a packet from ever being sent twice and
prevents the encoder from ever losing sync with the decoder.
The HS Series uses the CipherLinx™ algorithm, which is based on Skipjack, a
cipher designed by the U.S. National Security Agency (NSA). At the time of this
writing, there are no known cryptographic attacks on the full Skipjack algorithm.
Skipjack uses 80-bit keys to encipher 64-bit data blocks. The CipherLinx™
algorithm uses Skipjack in a provably secure authenticated encryption mode
both to protect the secrecy of the data and ensure that it is not modified by an
adversary. 8 bits of data are combined with a 40-bit counter and 80 bits of
integrity protection before being encrypted to produce each 128-bit packet.
The key is generated with the decoder by the user through multiple button
presses. This is ensures that the key is random and chosen from all 280 possible
keys. Since all of the keys are created by the user and are internal to the part,
there is no list of numbers anywhere that could be accessed to compromise the
system.
Preamble
128-Bit Encrypted Data
RX Noise Logic
Balancing Filter Filter
Integrity Check
80 bits
Data
8 bits
Counter
40 bits
Encryption of the transmitted data is only one factor in the security of a system.
With most systems, once an encoder is authorized to access a decoder, it can
activate all of the decoder data lines. With the HS Series, each encoder can be
set to only activate certain lines. This means that the same hardware can be set
up with multiple levels of control, all at the press of a button.
Figure 6: HS Series Data Structure
There are several methods an attacker may use to try to gain access to the data
or the secured area. Because a key is used to interpret an encrypted message,
trying to find the key is one way to attack the protected message. The attacker
would either try using random numbers or go through all possible numbers
sequentially to try to get the key and access the data. Because of this, it is
sometimes believed that a larger key size will determine the strength of the
encryption. This is not entirely true. Although it is a factor in the equation, there
are many other factors that need to be included to maintain secure encryption.
Another factor in system security is the control of the encoder. If attackers gain
control of the encoder, typically they would be able to access the system. The
HS offers the option of adding a Personal Identification Number (PIN) to the
encoder that must be entered before the encoder will activate. Furthermore,
since each encoder has its own key and the Control Permissions are stored in
the decoder, all the attackers would be able to do is duplicate the device that
they have already taken. They will not be able to grant themselves greater
authority, create a new controller, or replicate another encoder.
One factor is the way that the underlying cipher (in the case of the CipherLinx™
algorithm, Skipjack) is used to encrypt the data. This is referred to as the cipher’s
“mode of operation.” If a highly secure cipher is used in an insecure mode, the
resulting encryption will be insecure. For example, some encryption modes allow
an adversary to combine parts of legitimate encrypted messages together to
create a new (and possibly malicious) encrypted message. This is known as a
“cut-and-paste” attack. The mode of operation used by the CipherLinx™
algorithm is proven to prevent this type of attack.
Before the encoder sends a packet, it will calculate the Hamming Weight (the
number of ‘1’s in the string) of the packet to determine the duty cycle. If the duty
cycle is greater than 50% (more ‘1’s than ‘0’s), the encoder will logically invert all
of the bits. This ensures that every packet will always contain 50% or less ‘1’s.
Since the FCC allows transmitter output power to be averaged over 100mS, this
allows a legal improvement in link range and performance for many devices
using an ASK / OOK transmitter. A 50% duty cycle is generally the best
compromise between data volume and output power.
Another critical factor is how often the message changes. To prevent code
grabbing, most high-security systems send different data with each transmission.
Some remote control applications will encrypt the message once per activation
and repeat the same message over again until it is deactivated. This gives an
attacker the opportunity to copy the message and retransmit it to maintain the
state of the protected device and “hold the door open”, or worse yet, have the
option to come back later and gain access. The HS Series goes a step further
and sends different data with EACH PACKET, so the data will change
continuously during each transmission. This means that at 28,800bps, there will
be a completely new 128-bit message sent every 25.5mS.
Some other manufacturers may use a Pulse Width Modulation (PWM) scheme
or Manchester Encoding scheme to maintain a 50% duty cycle. Both of these
methods work, but are inefficient and do not make use of the full link budget. The
HS Series uses true serial data while maintaining a 50% duty cycle. Application
Note AN-00310 covers these issues in detail.
Page 8
Page 9
ENCODER OPERATION
Power Up
Upon power-up, the encoder sets the baud rate based on the state of the
SEL_BAUD line, pulls the TX_CNTL line low, and goes into a low-power sleep
mode. It will remain asleep until either the KEY_IN, SEND, or CREATE_PIN line
goes high. These lines place the encoder in either Get Key Mode, Send Mode,
or Create PIN Mode as described in the following sections.
Set Baud Rate
Pull The TX_CNTL
Line low
Go To Sleep &
Wake On Interrupt
ENCODER GET KEY MODE
When the encoder registers activity on the KEY_IN line, it will enter Get Key
Mode. In this mode, the encoder will look for an encryption key and user ID from
a decoder. When it receives this information, it will send a confirmation on the
DATA_OUT line to the decoder. It will then look for a final confirmation from the
decoder on the KEY_IN line. Once this confirmation is received, the encoder will
take the MODE_IND line high for one second to indicate that the key has been
successfully transferred and that the units may now work together.
Is The
KEY_IN Line
High?
Is The
CREATE_PIN
Line High?
Is The
SEND Line
High?
NO
NO
NO
YES
YES
YES
Pull The TX_CNTL
Line High
Set Timer
YES
NO
Is PIN
Active?
Is PIN
Enabled?
Pull The DATA
Line High
ENCODER SEND MODE
YES
YES
NO
Time Out?
When the SEND line goes high, the encoder will enter Send Mode. It will pull the
TX_CNTL line high to activate the transmitter and record the state of the data
lines. The encoder will then encrypt the data using the saved key and send it
through the DATA_OUT line. It will continue doing this for as long as the SEND
line is high, updating the state of the data lines with each transmission. Once
SEND is pulled low, the encoder will finish the current transmission, pull
TX_CNTL low to deactivate the transmitter, and go to sleep.
Get Data Byte
Create Packet
Set 15-Second
Timer
YES
Is PIN
Active?
NO
Toggle
MODE_IND Line
NO
Is The
KEY_IN Line
High?
NO
Pull The DATA
Line Low
Set Timer To 2S
15 Second
Timer Time
Out?
YES
YES
Send Packet
For simple applications that require only a single input, SEND can be tied directly
to the data input line, allowing a single connection. If additional lines are used in
this manner, diodes or dual contact switches will be necessary to prevent voltage
on one data line from activating all of the data lines. The Typical Applications
section of this data guide demonstrates the use of diodes for this purpose.
YES
Did The Timer
Expire?
NO
NO
Is The
Data Valid?
Is The
SEND Line
High?
YES
Is The
CREATE Line
High?
YES
NO
YES
Pull The TX_CNTL
Line High
NO
NO
Was A Button
Pressed?
NO
ENCODER CREATE PIN MODE
NO
Get Data
Is PIN
Enabled?
For higher security applications, the HS Series encoder has the option to set a
Personal Identification Number (PIN) to control access to the encoder. This PIN
is a four-digit combination of the eight data lines that must be entered before the
encoder will transmit any commands to the decoder.
NO
Was A Button
Pressed?
YES
YES
Was The
4th Button
Pressed?
NO
YES
NO
Is The
Data Valid?
Pull The TX_CNTL
Line Low
Create PIN Mode is entered by pressing the CREATE button on the encoder.
The MODE_IND line will begin flashing to indicate that the encoder is ready for
the PIN to be entered. The user will have 15 seconds to press any 4-button
combination to set the PIN. After the fourth button press, the MODE_IND line
will go low. If 4 buttons are not pressed or the CREATE line goes high within the
15 second window, no PIN will be set. Once created, the PIN can be erased only
by learning a new key from the decoder.
Was The
4th Button
Pressed?
NO
YES
YES
Set Timer From
SEL_TIMER Line
Did
Send And
Receive
Confirmation
Pass?
NO
Does PIN
Match?
YES
NO
Save PIN
Is The
SEND Line
High?
YES
YES
YES
Save Data
NO
Once the PIN has been set, the user must enter it correctly before the encoder
will transmit any commands. When entered, the encoder will be active for a
period of time set by the SEL_TIMER line. If this line is connected to ground, the
PIN will need to be entered after 15 minutes of inactivity. If this line is high, the
PIN will need to be entered after 30 seconds of inactivity. If no PIN is set, then
the encoder will activate as soon as the SEND line goes high.
Pull MODE_IND
High For 1 Second
NO
Did The Timer
Expire?
YES
Figure 7: HS Series Encoder Flowchart
Page 10
Page 11
TYPICAL APPLICATION
TYPICAL SYSTEM SETUP
The HS Series encoder is ideal for registering button presses in secure remote
control applications. An example application circuit is shown below.
The HS Series offers an unmatched combination of features and security, yet is
easy for system designers and end users to operate. To demonstrate this, let’s
take a brief look at a typical user setup followed by more detailed design
information. The Typical Applications sections of the encoder and decoder data
guides show the circuit schematics on which these examples are based.
100k
100k
100k
100k
100k
100k
1
2
3
4
5
6
7
8
9
20
19
18
17
16
15
14
13
12
11
LICAL-ENC-HS001
D6
D7
D5
D4
D3
D2
VCC
VCC
D1
D0
1. Create and exchange a key from a decoder to an encoder
SEL_BAUD
SEL_TIMER
GND
The high security key is created and exchanged by placing the decoder in the
Create Key Mode. The decoder’s MODE_IND line LED will light to indicate that
the decoder has entered Create Key Mode. The decoder’s CREATE_KEY button
is then pressed ten times to create the key. After the tenth press, the MODE_IND
LED will turn off and the decoder will send the key out of the KEY_OUT line. The
MODE_IND LED on the encoder will light to indicate that the key has been
successfully transferred.
GND
100k
100k
From Key Input Port
KEY_IN
To Transmitter PDN
TX_CNTL
DATA_OUT
MODE_IND
220
To Transmitter
SEND
CREATE_PIN
100k
220
10
100k
2. Establish Control Permissions
The user establishes what buttons on the encoder will be recognized by pressing
the decoder LEARN button. The decoder’s MODE_IND LED will start flashing
and the user presses the buttons that will be allowed access. Control
Permissions are stored when the LEARN button is pressed again or
automatically after 17 seconds.
Figure 8: HS Series Encoder Application Circuit
In this example, the data lines are connected to buttons, and when any button is
pressed, the SEND line is pulled high and causes the encoder to transmit.
Diodes are used to prevent the voltage on one data line from affecting another.
The KEY_IN line is attached to a port that allows the key to be transferred from
the decoder during setup. To ensure security, this would normally be a wire,
contact, or short range IR link, although any connection capable of transferring
asynchronous serial data may be utilized.
There are other powerful options such as programming a user PIN or copying a
decoder but these simple steps are all that is required for a typical setup. It is
really that simple for a manufacturer or end user to setup the product!
DESIGN STEPS TO USING THE HS SERIES
Key creation and exchange from a decoder to an encoder
None of the inputs have pull-up or pull-down resistors internally, so 100kΩ pull-
down resistors are used on the data, SEND, and CREATE_PIN lines. These
resistors are used to pull the lines to ground when the buttons are not being
pressed, which ensures that the pins are always in a known state and not
floating. Without these resistors, the state of the lines cannot be guaranteed and
encoder operation may not be predictable.
2
DATA OUT
DATA IN
4
MODE_IND
A LED is attached to the MODE_IND line to provide visual feedback to the user
that an operation is taking place. This line will source a maximum of 25mA, so
the limiting resistor may not be needed, depending on the LED chosen and the
brightness desired. A LED can also be connected to the TX_CNTL line to provide
visual indication that the encoder is sending data.
CREATE KEY BUTTON
LEARN BUTTON
3
SEND COPY BUTTON
1
KEY IN
KEY OUT
Figure 9: Steps to Exchange a Key
Outgoing encrypted data will be sent via the DATA_OUT line at the baud rate
determined by the state of the SEL_BAUD line. In the circuit above, the baud has
been set for 4,800bps by pulling it to ground. The DATA_OUT line can be
connected directly to the DATA_IN line of a Linx transmitter or other wireless
device.
1. Provide a serial data connection from the decoder’s KEY_OUT line to the
encoder’s KEY_IN line. Typically this would be a wire, contact, or infrared.
2. Provide a serial data connection from the encoder’s DATA_OUT line to the
decoder’s DATA_IN line. Typically, this would be a wireless connection using a
transmitter and receiver combination.
The TX_CNTL line may be connected to the PDN line of a Linx transmitter so
that the module will enter a low power state when not in use.
3. On the decoder, set the LEARN line high and then the CREATE_KEY line high
to enter Create Key Mode. Take the LEARN line low, and toggle the
CREATE_KEY line high and low ten times to generate the key.
In this example, the data lines are pulled high by simple pushbutton switches, but
many other methods may be employed. Contacts, reed switches, or
microcontrollers are just some examples of other ways to pull the data lines high.
The flexibility of the encoder, combined with the associative options of the
matching decoder, opens a new world of options for creative product designers.
4. The encoder and decoder will automatically exchange the key using the
DATA_OUT / DATA_IN and KEY_OUT / KEY_IN lines. If the key exchange is
successful, the decoder and encoder MODE_IND lines will go high for 1 second.
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DESIGN STEPS TO USING THE HS SERIES (CONT.)
ONLINE RESOURCES
Creation of Control Permissions
®
DATA OUT
DATA IN
www.linxtechnologies.com
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MODE_IND
2
4
CREATE KEY BUTTON
LEARN BUTTON
1
3
SEND COPY BUTTON
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KEY IN
KEY OUT
• Application Notes
• Knowledgebase
• Software Updates
Figure 10: Steps to Create Control Permissions
1. On the decoder, set the LEARN line high, then take it low to enter Learn Mode.
2. While the decoder’s MODE_IND line is toggling high / low, set a data line on the
encoder high, then low. Repeat for each line to which permission will be granted.
If you have questions regarding any Linx product and have Internet access,
make www.linxtechnologies.com your first stop. Our website is organized in an
intuitive format to immediately give you the answers you need. Day or night, the
Linx website gives you instant access to the latest information regarding the
products and services of Linx. It’s all here: manual and software updates,
application notes, a comprehensive knowledgebase, FCC information, and much
more. Be sure to visit often!
3. After all the desired data lines have been selected, set the LEARN line high,
then low again, or wait until the 17-second time-out occurs. The permissions will
now be saved in the decoder.
4. Select the data lines during an actual transmission to confirm that the
permissions have been successfully created.
USING THE OPTIONAL ENCODER PIN
Creation of an encoder PIN
1. Set the CREATE line high, then low to enter Create
PIN Mode. The MODE_IND line will begin toggling
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high / low until either a PIN is successfully entered
or 15 seconds has passed.
MODE_IND
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2. To enter the PIN, set high then low a sequence of
2
any four data lines. The MODE_IND will stop
4
}
toggling and the PIN will be created.
3. To cancel the Create PIN Mode prior to the fourth
entry, either wait for the 15 second timeout to pass
or set and clear the CREATE line. The MODE_IND
will stop toggling and no PIN will be created.
1
CREATE
KEY IN
3
4. If a new KEY is created, the PIN will be Figure 11: Encoder PIN Setup
automatically erased.
Using the PIN
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1. The PIN is entered by setting each data line high, then taking it low until all four
entries have been made. There is a maximum 2-second time limit between
entries after which the PIN must be reentered in its entirety.
Through its Connector City division, Linx offers a wide
selection of high-quality RF connectors, including FCC
compliant types such as RP-SMAs that are an ideal
match for our modules and antennas. Connector City
focuses on volume OEM requirements, which allows
standard and custom RF connectors and cable
assemblies to be offered at a low cost.
2. Once the PIN is successfully entered, the encoder will be operational unless it
is inactive for a period longer than what is chosen by the SEL_TIMER line, in
which case PIN reentry would be necessary.
Page 14
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WIRELESS MADE SIMPLE ®
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FAX: (541) 471-6251
www.linxtechnologies.com
Disclaimer
Linx Technologies is continually striving to improve the quality and function of its products. For this reason,
we reserve the right to make changes to our products without notice. The information contained in this
Overview Guide is believed to be accurate as of the time of publication. Specifications are based on
representative lot samples. Values may vary from lot-to-lot and are not guaranteed. "Typical" parameters can
and do vary over lots and application. Linx Technologies makes no guarantee, warranty, or representation
regarding the suitability of any product for use in any specific application. It is the customer's responsibility
to verify the suitability of the part for the intended application. NO LINX PRODUCT IS INTENDED FOR USE
IN ANY APPLICATION WHERE THE SAFETY OF LIFE OR PROPERTY IS AT RISK.
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© 2008 by Linx Technologies, Inc. The stylized Linx logo,
Linx, “Wireless Made Simple”, CipherLinx, and the stylized
CL logo are the trademarks of Linx Technologies, Inc.
Printed in U.S.A.
Certain products and methods presented
in this Data Guide are protected by one
or more patents pending.
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