HCS361-IP Microchip Technology, HCS361-IP Datasheet - Page 3

• Manufacturer Part Number: HCS361-IP
• Description: KEELOQ CODE HOPPING ENCODER
• Manufacturer: Microchip Technology

Before a transmitter can be used with a particular
receiver, the transmitter must be ‘learned’ by the
receiver. Upon learning a transmitter, information is
the transmitter. If a receiver receives a message of valid
FIGURE 1-1:
FIGURE 1-2:
FIGURE 1-3:
stored by the receiver so that it may track the
transmitter, including the serial number of the
transmitter, the current synchronization value for that
transmitter and the same encryption key that is used on
1996 Microchip Technology Inc.
EEPROM Array
Decryption Key
Serial Number
Sync Counter
Manufacturer’s
Manufacturer Code
Code
EEPROM Array
CREATION AND STORAGE OF ENCRYPTION KEY DURING PRODUCTION
BASIC OPERATION OF TRANSMITTER (ENCODER)
BASIC OPERATION OF RECEIVER (DECODER)
Decryption Key
Serial Number
Sync Counter
Button Press
Information
Serial Number or
Encryption
Algorithm
K
Transmitter
EE
Generation
Algorithm
L
Seed
Received Information
OQ
Key
Serial Number
Check for
Match
Preliminary
Encrypted Data
32 Bits of
Encryption
format, the serial number is checked and, if it is from a
learned transmitter, the message is decrypted and the
decrypted synchronization counter is checked against
what is stored. If the synchronization value is verified,
then the button status is checked to see what operation
is needed. Figure 1-3 shows the relationship between
some of the values stored by the receiver and the val-
ues received from the transmitter.
Encrypted Data
Key
Decryption
Algorithm
32 Bits of
K
EE
Transmitted Information
L
OQ
Serial Number
HCS361 EEPROM Array
Synchronization
Serial Number
Encryption Key
Sync Counter
Check for
Decrypted
Match
Counter
.
.
.
Button Press
Information
HCS361
DS40146C-page 3