100 m rolling code remote transmitter principle

The traditional security products for one-way transmission mainly use fixed-coded integrated circuits, such as PT2262, PT2272 and other codec chips. However, due to the limited encoding length of such codec chips, the code format is fixed. It is very easy to capture in the air. Radio wave code words and scanning and tracking methods can only be used in places where the security requirements are not high.

Microchip's KEELOQ-based HCS series of rolling code encoding chips overcome the shortcomings of the above systems and have been successfully applied in various security products. Because of the advanced nonlinear bit encryption technology used before the transmission of the code, Extremely confidential scrolling code. Each time the code is sent is unique, irregular, and non-repeating, so that any deciphering means such as illegal capture and scan tracking are turned into bubbles. It is very suitable for gates, garages, banks. Such as management systems; automatic burglar alarm system, identification, smart IC card and other fields.

100 m rolling code 433 MHz transmitter (including A27 battery section)

Second, HCS301 coded integrated circuit features:

1, confidentiality programmable 28Bit serial number, programmable 64Bit encryption key, each time the code is sent, the encryption key is not readable

2, internal characteristics wide range of operating voltage (HCS300 2.0V-6.3V, HCS301 5.5V-13.0V)

3, four function input ports (can be combined into 15 functions)

4, low voltage detection indicators

Third, the principle of HCS301 encoder

The HCS301 must generate a unique encryption key before use. The key generation process (Figure 1): The unique encryption password is formed by the key generation algorithm by the factory code and the serial number, and then written into the on-chip EPROM. Factory code. Also known as serial code or manufacturer code, the length is 64Bit. Each manufacturer is different, it is used to generate a unique encryption key corresponding to each encoder. Factory code is the key to the security of the whole system, should be standardized management , save. If the factory code leaks, the entire system does not have any security. The serial number is 28Bit, corresponding to each encoder, can be used as the user code.

The HCS301 encoding process is encrypted by the KEELOQ algorithm, such as the original code, encryption key and synchronization code. It generates a 32Bit highly confidential rolling code. Due to the complexity of the KEELOQ algorithm and the 16-bit synchronization code, each time it is transmitted, it is updated. The secondary transmission code is completely different from the previous one. It can only be repeated after 216 transmissions, and 10 times of code calculation every day, with an interval of 18 years.

The HCS301 has 192Bit (16&TImes; 12) EEPROM for storing encryption keys, serial number synchronization values ​​and other information. It needs to be operated before and during use of the HCS300/301. It needs to be used before use. Programming. For the sake of confidentiality, the readback check can only be performed within a relatively short time after programming the EEPROM. Other times are forbidden. During use, the EEPROM information is encrypted, the transmitted code is generated, and the sync value is updated.

The transmission information of HCS301 consists of several parts. The codeword of each code starts with the guide code mark and the header, then the rolling code and the fixed code part, and finally the protection time of each transmission. The rolling code part is 32Bit. Encrypted data; fixed code part is 34Bit, including status bit, function bit and 28-digit serial number. The total code combination is up to 7.38 & TImes; 1019 times.

The HCS301 transmits 66-bit encoded data when each button is pressed. Due to the rolling code and the fixed code, the rolling code portion is composed of 4 button states, 2 bits for overflow bits, 10 bits for authentication bits and 16 bits for synchronization values ​​are encrypted. Generated. The fixed code consists of a 28-bit serial number, a 4-bit button state, and a 2-bit status bit.