HCS410 datasheet(22/46 Pages) MICROCHIP

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HCS410

DS40158F-page 22

4.0

INTEGRATING THE HCS410

INTO A SYSTEM

Use of the HCS410 in a system requires a compatible

decoder. This decoder is typically a microcontroller with

compatible firmware. Firmware routines that accept

transmissions from the HCS410, decrypt the code hop-

ping portion of the data stream and perform IFF func-

tions are available. These routines provide system

designers the means to develop their own decoding

system.

4.1

Key Generation

The serial number for each transmitter is programmed

by the manufacturer at the time of production. The

generation of the encoder key is done using a key gen-

eration algorithm (Figure 4-1). Typically, inputs to the

key generation algorithm are the serial number of the

transmitter or seed value, and a 64-bit manufacturer’s

code. The manufacturer’s code is chosen by the sys-

tem manufacturer and must be carefully controlled. The

manufacturer’s code is a pivotal part of the overall

system security.

FIGURE 4-1:

CREATION AND STORAGE OF ENCODER KEY DURING PRODUCTION

Transmitter

Manufacturer’s

Serial Number or

Code

Encoder

Key

Generation

Algorithm

Serial Number

Encoder Key

Sync Counter

HCS410 EEPROM Array

Seed

40158F.book Page 22 Wednesday, June 1, 2011 10:36 AM

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