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PDF HCS201 Data sheet ( Hoja de datos )
| Número de pieza | HCS201 | |
| Descripción | KEELOQ Code Hopping Encoder | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de HCS201 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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HCS201
KEELOQ® Code Hopping Encoder
FEATURES
Security
• Programmable 28-bit serial number
• Programmable 64-bit encryption key
• Each transmission is unique
• 66-bit transmission code length
• 32-bit hopping code
• 34-bit fixed code (28-bit serial number,
4-bit button code, 2-bit status)
• Encryption keys are read protected
Operating
• 3.5V-13V operation
(2.0V min. using the Step up feature)
• Three button inputs
• 7 functions available
• Selectable baud rate
• Automatic code word completion
• Battery low signal transmitted to receiver
• Non-volatile synchronization data
Other
• Simple programming interface
• On-chip EEPROM
• On-chip oscillator and timing components
• Button inputs have internal pull-down resistors
• Minimum component count
• Synchronous Transmission mode
• Built-in step up regulator
Typical Applications
• The HCS201 is ideal for Remote Keyless Entry
(RKE) applications. These applications include:
• Automotive RKE systems
• Automotive alarm systems
• Automotive immobilizers
• Gate and garage door openers
• Identity tokens
• Burglar alarm systems
DESCRIPTION
The HCS201 from Microchip Technology Inc. is a code
hopping encoder designed for secure Remote Keyless
Entry (RKE) systems. The HCS201 utilizes the KEELOQ
code hopping technology, incorporating high security, a
small package outline and low cost. The HCS201 is a
perfect solution for unidirectional remote keyless entry
systems and access control systems.
PACKAGE TYPES
PDIP, SOIC
S0 1
S1
S2
VDDB
2
3
4
8 VDD
7 STEP
6 DATA
5 VSS
HCS201 BLOCK DIAGRAM
VDDB
VDD Step Up
Controller
Oscillator
RESET circuit
Controller
Power
latching
and
switching
STEP
EEPROM
Encoder
DATA
VSS
VDD
32-bit shift register
Button input port
S2 S1 S0
The HCS201 combines a 32-bit hopping code,
generated by a nonlinear encryption algorithm, with a
28-bit serial number and 6 information bits to create a
66-bit code word. The code word length eliminates the
threat of code scanning and the code hopping mecha-
nism makes each transmission unique, thus rendering
code capture and resend schemes useless.
© 2001 Microchip Technology Inc.
DS41098C-page 1
1 page  
2.0 ENCODER OPERATION
As shown in the typical application circuits (Figure 2-1),
the HCS201 is a simple device to use. It requires only
the addition of buttons and RF circuitry for use as the
transmitter in your security application. A description of
each pin is given in Table 2-1.
FIGURE 2-1:
VDD
TYPICAL CIRCUITS
B0 S0 VDD
B1 S1 STEP
S2 DATA
VDDB
VSS
Tx out
Two button remote control
B3 B2 B1 B0
VDD
S0
S1
S2
VDDB
VDD
STEP
DATA
VSS
Four button remote control
Tx out
VDD
S0
S1
S2
VDDB
2.0-6.0V
VDD
STEP
DATA
VSS
R
Tx out
L
D
Q
C
Three button remote control with Step up regulator
External components sample values:
R = 5.1 KΩ
L = 390 uH
Q = 2N3904
C = 1.0 uF
D = ZHCS400CT (40V 0.4A Zetex)
(see Section 5.6 for a description of the Step Up circuit)
Note:
Up to 7 functions can be implemented by pressing
more than one button simultaneously or by using a
suitable diode array.
HCS201
TABLE 2-1: PIN DESCRIPTIONS
Pin Pin
Name Number
Pin Description
S0 1 Switch input 0
S1 2 Switch input 1
S2 3 Switch input 2 / Clock pin for
Programming mode
VDDB
4 Battery input pin, supplies power
to the step up control circuitry
VSS 5 Ground reference connection
DATA
6 Pulse Width Modulation (PWM)
output pin / Data pin for
Programming mode
STEP 7 Step up regulator switch control
VDD 8 Positive supply voltage
The HCS201 will wake-up upon detecting a button
press and delay approximately 10 ms for button
debounce (Figure 2-2). The synchronization counter,
discrimination value and button information will be
encrypted to form the hopping code. The hopping code
portion will change every transmission, even if the
same button is pushed again. A code word that has
been transmitted will not repeat for more than 64K
transmissions. This provides more than 18 years of use
before a code is repeated; based on 10 operations per
day. Overflow information sent from the encoder can be
used to extend the number of unique transmissions to
more than 192K.
If in the transmit process it is detected that a new but-
ton(s) has been pressed, a RESET will immediately
occur and the current code word will not be completed.
Please note that buttons removed will not have any
effect on the code word unless no buttons remain
pressed; in which case the code word will be completed
and the power-down will occur.
© 2001 Microchip Technology Inc.
DS41098C-page 5
5 Page 
HCS201
5.0 SPECIAL FEATURES
5.1 Code Word Completion
The code word completion feature ensures that entire
code words are transmitted, even if the button is
released before the code word is complete. If the but-
ton is held down beyond the time for one code word,
multiple code words will result. If another button is acti-
vated during a transmission, the active transmission
will be aborted and a new transmission will begin using
the new button information.
5.2 VLOW: Voltage LOW Indicator
The VLOW bit is transmitted with every transmission
(Figure 8-4) and will be transmitted as a one if the
operating voltage has dropped below the low voltage trip
point. The trip point is selectable based on the battery
voltage being used. See Section 3.7.2 for a description
of how the low voltage select option is set. This VLOW
signal is transmitted so the receiver can give an audible
signal to the user that the transmitter battery is low.
5.3 Auto-Shutoff
The auto-shutoff function automatically stops the device
from transmitting if a button inadvertently gets pressed
for a long period of time. This will prevent the device from
draining the battery if a button gets pressed while the
transmitter is in a pocket or purse. Time-out period is TTO.
5.4 Seed Transmission
In order to increase the level of security in a system, it
is possible for the receiver to implement what is known
as a secure learn function. This can be done by utilizing
the seed value stored in EEPROM, transmitted only
when all three button inputs are pressed at the same
time (Table 5-1). Instead of the normal key generation
inputs being used to create the crypt key, this seed
value is used.
TABLE 5-1: PIN ACTIVATION TABLE
Standby
Hopping Code
Seed Code
Function S2 S1 S0
0 000
1 001
2 010
- ---
5 101
6 110
7 111
5.5 Blank Alternate Code Word
Federal Communications Commission (FCC) part 15
rules specify the limits on worst case average funda-
mental power and harmonics that can be transmitted in
a 100 ms window. For FCC approval purposes, it may
therefore be advantageous to minimize the transmis-
sion duty cycle. This can be achieved by minimizing the
duty cycle of the individual bits as well as by blanking
out consecutive code words. Blank Alternate Code
Word (BACW) may be used to reduce the average
power of a transmission by transmitting only every sec-
ond code word (Figure 5-1). This is a selectable feature
that is determined in conjunction with the baud rate
selection bit BSL0.
Enabling the BACW option may likewise allow the user
to transmit a higher amplitude transmission as the time
averaged power is reduced. BACW effectively halves
the RF on time for a given transmission so the RF out-
put power could theoretically be doubled while main-
taining the same time averaged output power.
FIGURE 5-1:
BLANK ALTERNATE CODE WORD (BACW)
Amplitude
BRS = 0
A
Code Word
Code Word
Code Word
Code Word
BRS = 1
2A
Time
© 2001 Microchip Technology Inc.
DS41098C-page 11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet HCS201.PDF ] | |
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