HCS512-IP Microchip Technology, HCS512-IP Datasheet - Page 12

• Manufacturer Part Number: HCS512-IP
• Description: KEELOQ CODE HOPPING DECODER
• Manufacturer: Microchip Technology

HCS512
7.3
There are two key generation algorithms implemented in the HCS512 decoder. The K
vides a higher level of security than the XOR algorithm. Section 6.1 describes the selection of the algorithms in the con-
figuration byte.
7.3.1
This algorithm uses the K
Key
Key
7.3.2
The two 32-bits seeds are XOR with the manufacturer’s code to form the 64 bit encoder key.
Key
Key
After programming the manufacturer’s code, the HCS512 decoder will automatically activate an Erase All function,
removing all transmitters from the system.
If LRNIN is taken low momentarily during the learn status indication, the indication will be terminated. Once a successful
learning sequence is detected, the indication can be terminated, allowing quick learning in a manufacturing set up.
FIGURE 7-2:
DS40151C-page 12
Upper 32 bits
Lower 32 bits
Upper 32 bits
Lower 32 bits
Padding
Padding
Padding
Padding
0000b
0000b
2/2B
6/65
Key Generation Algorithms
K
XOR WITH THE MANUFACTURER’S CODE
LS 32 bits of Seed Transmission
EE
LS 32 bits of Seed Transmission
L
OQ
MS 28 bits of Seed Transmission
MS 28 bits of Seed Transmission
= F
= SourceL
28/24-bit Serial Number
28/24-bit Serial Number
= F
= SourceH
DECRYPT ALGORITHM
HCS512 KEY GENERATION
SC_LRN = 1
SC_LRN = 0
K
K
EE
EE
L
L
OQ
OQ
EE
Decrypt
Decrypt
L
OQ
Manufacturers Code |
Manufacturers Code |
decryption algorithm and the manufacturer’s code to derive the encoder key as follows:
(SourceL) |
(SourceH) |
64 Bit Manufacturers Code
64 Bit Manufacturers Code
Lower 32 bits
Upper 32 bits
Decryption
Decryption
Algorithm
LRN0 = 0
Algorithm
K
LRN0 = 1
K
EE
EE
XOR
L
L
OQ
OQ
LS 32 bits of Encoder Key
MS 32 bits of Encoder Key
MS 32 bits of Encoder Key
LS 32 bits of Encoder Key
LS 32 bits of Encoder Key
MS 32 bits of Encoder Key
EE
L
OQ
1997 Microchip Technology Inc.
decryption algorithm pro-