MCS3142-ISLASHST datasheet(20/37 Pages) MICROCHIP

20 / 37 page

MCS3142

DS40001747A-page 20

 2014 Microchip Technology Inc.

5.10

Code Word Format

The Ultimate KEELOQ technology code word is 192 bits

long. It comprises three sections (see Figure 5-2):

• 32 bits of the encoder’s serial number

• 128 bits of the encrypted hopping code

• 32 bits of authorization code

These segments are described in detail in the following

sections.

FIGURE 5-2:

ULTIMATE KEELOQ® CODE WORD FORMAT

5.10.1

HOPPING CODE PORTION

The hopping portion of an Ultimate KEELOQ code word

contains nearly all of the transmitted data. The

time-stamp and Button Timer ensure that each

transmission is unique.

5.10.2

FIXED CODE PORTION

The fixed, unencrypted portion of an Ultimate KEELOQ

code word consists of the encoder’s serial number.

Unlike Classic KEELOQ, there is no copy of the function

code.

5.10.3

AUTHORIZATION CODE

The 32-bit Authorization Code is appended after the

hopping portion of the code word.

5.11

Seed Word Format

The seed word is used when pairing the transmitter to

a receiver using a secure learn methodology.

FIGURE 5-3:

ULTIMATE KEELOQ® SEED WORD FORMAT

Ser ial Numbe r

Delta

Time

32 bits

Fixe d P ortion

Rev. 20-000 009A

8/29/201 3

128 bits En crypted Ho pping Code

Authori zation

Code

32 bits

Auth Portion

Sync

Counter

Battery

Functio n

Code

Low Spee d

Timestamp

Button

Timer

Resync

Counter

32-bits

24-bits

8-bits

32-bits

16-bits

32-bits

Serial Number

Seed

32 bits

Fixed Portion

Rev. 20-000010A

10/2/2013

128 bit Seed

Authorization

Code

32 bits

Auth Portion

Note:

In the Seed code word, the serial number is sent as

0xFFFFFFFF.

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