hcs515 Microchip Technology Inc., hcs515 Datasheet - Page 17

• Manufacturer Part Number: hcs515
• Description: Keeloq Code Hopping Decoder Keeloq Code Hopping Decoder
• Manufacturer: Microchip Technology Inc.

6.0
The HCS515 supports two learning schemes which are selected during the initialization of the system EEPROM. The
learning schemes are:
• Normal learn using the K
• Secure learn using the K
6.1
This learning scheme uses the K
the encoder decryption key. The 28-bit serial number is patched with predefined values as indicated below to form two
32-bit seeds.
Then, using the K
derived as follows:
6.2
This scheme uses the secure seed transmitted by the encoder to derive the two input seeds. The decoder always uses
the lower 64 bits of the transmission to form a 60-bit seed. The upper 4 bits are always forced to zero.
For 32-bit seed encoders:
For 48-bit seed encoders:
For 60-bit seed encoders:
The K
follows:
2002 Microchip Technology Inc.
SourceH = 60000000 00000000H + Serial Number |
SourceL = 20000000 00000000H + Serial Number |
KeyH
KeyL
SourceH = Serial Number
SourceL = Seed
SourceH = Seed
SourceL = Seed
SourceH = Seed
SourceL = Seed
KeyH
KeyL
EE
L
KEY GENERATION
Normal (Serial Number derived) Learn using the Decryption Algorithm
Secure (Seed Derived) Learn using the Decryption Algorithm
OQ
Lower 32 bits
Lower 32 bits
Upper 32 bits
Upper 32 bits
decryption algorithm and the manufacturer’s code is used to derive the encoder decryption key as
EE
32 bits
Lower 32 bits
Lower 32 bits
= F
= Decrypt (SourceL)
Upper 16 bits
Upper 28 bits
= F
= Decrypt (SourceH)
L
OQ
K
K
EE
EE
EE
EE
decryption algorithm and the manufacturer’s code the encoder decryption key is
L
L
L
L
OQ
OQ
OQ
OQ
Lower 28 bits
Decryption
Decryption
EE
+ Serial Number
with upper 4 bits set to zero
decryption algorithm
decryption algorithm
L
OQ
decryption algorithm and the 28-bit serial number of the transmitter to derive
(SourceL) |
(SourceH) |
64-bit Manufacturer’s Code
64-bit Manufacturer’s Code
Upper 16 bits
64-bit Manufacturer’s Code
64-bit Manufacturer’s Code
28 bits
28 bits
(with upper 4 bits set to zero) << 16
HCS515
DS40183D-page 17