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PDF HCS301 Data sheet ( Hoja de datos )
| Número de pieza | HCS301 | |
| Descripción | KEELOQ CODE HOPPING ENCODER | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de HCS301 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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HCS301
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 - 13.0V operation
• Four button inputs
• No additional circuitry required
• 15 functions available
• Selectable baud rate
• Automatic code word completion
• Battery low signal transmitted to receiver
• Battery low indication on LED
• Non-volatile synchronization data
Other
• Functionally identical to HCS300
• Easy-to-use programming interface
• On-chip EEPROM
• On-chip oscillator and timing components
• Button inputs have internal pull-down resistors
• Current limiting on LED output
• Low external component cost
Typical Applications
The HCS301 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 HCS301 from Microchip Technology Inc. is a code
hopping encoder designed for secure Remote Keyless
Entry (RKE) systems. The HCS301 utilizes the KEELOQ
code hopping technology, which incorporates high
security, a small package outline and low cost, to make
this device a perfect solution for unidirectional remote
keyless entry systems and access control systems.
PACKAGE TYPES
PDIP, SOIC
S0 1
S1 2
S2 3
S3 4
8 VDD
7 LED
6 PWM
5 VSS
HCS301 BLOCK DIAGRAM
Oscillator
LED
RESET circuit
LED driver
Controller
Power
latching
and
switching
PWM
EEPROM
Encoder
32-bit shift register
VSS
VDD
Button input port
S3 S2 S1 S0
The HCS301 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.
DS21143B-page 1
1 page  
2.0 DEVICE OPERATION
As shown in the typical application circuits (Figure 2-1),
the HCS301 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.
Note:
When VDD > 9.0V and driving low capaci-
tive loads, a resistor with a minimum value
of 50Ω should be used in line with VDD.
This prevents clamping of PWM at 9.0V in
the event of PWM overshoot.
FIGURE 2-1:
TYPICAL CIRCUITS
+12V
R (2)
B0 S0 VDD
B1 S1 LED
S2 PWM
S3 VSS
Tx out
2 button remote control
B4 B3 B2 B1 B0
+12V
R (2)
S0 VDD
S1 LED
S2 PWM
S3 VSS
5 button remote control (1)
Tx out
Note 1: Up to 15 functions can be implemented by pressing
more than one button simultaneously or by using a
suitable diode array.
2: Resistor R is recommended for current limiting.
HCS301
TABLE 2-1: PIN DESCRIPTIONS
Name
Pin
Number
Description
S0
S1
S2
S3
VSS
PWM
LED
VDD
1 Switch input 0
2 Switch input 1
3 Switch input 2 / Clock pin when in
Programming mode
4 Switch input 3
5 Ground reference
6 Pulse Width Modulation (PWM)
output pin / Data pin for
Programming mode
7 Cathode connection for LED
8 Positive supply voltage
The HCS301 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.
DS21143B-page 5
5 Page 
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 LED Output Operation
During normal transmission the LED output is LOW. If
the supply voltage drops below the low voltage trip
point, the LED output will be toggled at approximately
5Hz during the transmission (Section 3.6.4).
5.3 RPT: Repeat Indicator
This bit will be low for the first transmitted word. If a
button is held down for more than one transmitted code
word, this bit will be set to indicate a repeated code
word and remain set until the button is released.
5.4 VLOW: Voltage LOW Indicator
The VLOW signal is transmitted so the receiver can give
an indication to the user that the transmitter battery is
low. The VLOW bit is included in every transmission
(Figure 4-2 and Figure 8-5) and will be transmitted as a
zero if the operating voltage is above the low voltage
trip point. Refer to Figure 4-2. The trip point is select-
able based on the battery voltage being used. See Sec-
tion 3.6.3 for a description of how the low voltage trip
point is configured.
5.5 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.
This function can be enabled or disabled and is
selected by setting or clearing the Auto-shutoff bit (see
Section 3.4.1). Setting this bit high will enable the func-
tion (turn Auto-shutoff function on) and setting the bit
low will disable the function. Time-out period is approx-
imately 25 seconds.
HCS301
5.6 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
Function S3 S2 S1
Standby
0 000
1 000
Hopping Code
2
-
001
---
13 1 1 0
14 1 1 1
Seed Code 15 1 1 1
S0
0
1
0
-
1
0
1
© 2001 Microchip Technology Inc.
DS21143B-page 11
11 Page | ||
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| PDF Descargar | [ Datasheet HCS301.PDF ] | |
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