hcs412 Microchip Technology Inc., hcs412 Datasheet - Page 2

• Manufacturer Part Number: hcs412
• Description: Keeloq? Code Hopping Encoder And Transponder
• Manufacturer: Microchip Technology Inc.

HCS412
GENERAL DESCRIPTION
The HCS412 combines patented K
ping technology with bi-directional transponder chal-
lenge-and-response security into a single chip solution
for logical and physical access control.
When used as a code hopping encoder, the HCS412 is
ideally suited to keyless entry systems; vehicle and
garage door access in particular. The same HCS412
can also be used as a secure bi-directional transponder
for contactless token verification. These capabilities
make the HCS412 ideal for combined secure access
control and identification applications, dramatically
reducing the cost of hybrid transmitter/transponder
solutions.
1.0
Key Terms
The following is a list of key terms used throughout this
data sheet. For additional information on terminology,
please refer to the K
(TB003).
• RKE - Remote Keyless Entry.
• PKE - Passive Keyless Entry.
• Button Status - Indicates what transponder but-
• Code Hopping - A method by which a code,
• Code word - A block of data that is repeatedly
• Transmission - A data stream consisting of
• Crypt key - A unique and secret 64-bit number
• Encoder - A device that generates and encodes
• Encryption Algorithm - A recipe whereby data is
• Decoder - A device that decodes data received
• Transponder Reader (Reader, for short) - A
• Decryption algorithm - A recipe whereby data
DS41099C-page 2
ton input(s) activated the transmission. Encom-
passes the 4 button status bits LC0, S2, S1 and
S0 (Figure 3-2).
viewed externally to the system, appears to
change unpredictably each time it is transmitted
(Section 1.1.3).
transmitted upon button activation (Section 3.2).
repeating code words.
used to encrypt and decrypt data. In a symmetri-
cal block cipher such as the K
the encryption and decryption keys are equal and
will therefore be referred to generally as the crypt
key.
data.
scrambled using a crypt key. The data can only be
interpreted by the respective decryption algorithm
using the same crypt key.
from an encoder.
device that authenticates a token using bi-direc-
tional communication.
scrambled by an encryption algorithm can be
unscrambled using the same crypt key.
SYSTEM OVERVIEW
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introductory Technical Brief
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algorithm,
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code hop-
Preliminary
• Learn – Learning involves the receiver calculating
• Manufacturer’s code - A unique and secret 64-
• Anticollision - A scheme whereby transponders
• IFF - Identify Friend or Foe (Section 1.2).
• Proximity Activation - A method whereby an
• Transport code - An access code, ‘password’
• AGC - Automatic Gain Control.
the transmitter’s appropriate crypt key, decrypting
the received hopping code and storing the serial
number, synchronization counter value and crypt
key in EEPROM (Section 6.1). The K
uct family facilitates several learning strategies to
be implemented on the decoder. The following are
examples of what can be done.
- Simple Learning
- Normal Learning
- Secure Learn
bit number used to generate unique encoder crypt
keys. Each encoder is programmed with a crypt
key that is a function of the manufacturer’s code.
Each decoder is programmed with the manufac-
turer code itself.
in the same field can be addressed individually
preventing simultaneous response to a command
(Section 4.3.1).
encoder automatically initiates a transmission in
response to detecting an inductive field
(Section 4.4.1).
known only by the manufacturer, allowing pro-
gram access to certain secure device memory
areas (Section 4.3.3).
The receiver uses a fixed crypt key, common
to all components of all systems by the same
manufacturer, to decrypt the received code
word’s encrypted portion.
The receiver uses information transmitted
during normal operation to derive the crypt
key and decrypt the received code word’s
encrypted portion.
The transmitter is activated through a special
button combination to transmit a stored 60-bit
seed value used to generate the transmitter’s
crypt key. The receiver uses this seed value
to derive the same crypt key and decrypt the
received code word’s encrypted portion.
2002 Microchip Technology Inc.
EE
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prod-