4.1.1 Encrypted Code Portion

The encrypted portion of the classic KeeLoq packet contains:

16-bit synchronization counter. This value is used to create the hopping code. This value is incremented after each button press.
12 discrimination bits. These are the 12 LSb of the serial number. This value is used as post decryption check.
4-bit function code. Indicating the buttons pressed on the encoder. This value is also sent in the fixed portion and can be used for post decryption check.

The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.