The HCS370 is a code hopping encoder designed for secure Remote Keyless Entry (RKE) systems. The HCS370 utilizes Microchip’s patented KEELOQ? hopping technology, which incorporates high security, a small package outline, and low cost, to make this device a perfect solution for unidirectional remote keyless entry systems and access control systems. The HCS370 combines a 32-bit hopping code generated by a non-linear encryption algorithm, with a 28/32-bit serial number and 5/3 status bits to create a 69-bit transmission stream. The length of the transmission eliminates the threat of code scanning and the code hopping mechanism makes each transmission unique, thus rendering code capture and re-send (code grabbing) schemes useless. The encoder key, serial number, and configuration data are stored in EEPROM, which is not accessible via any external connection. This makes the HCS370 a very secure unit. The HCS370 provides an easy-to-use serial interface for programming the necessary security keys, system parameters, and configuration data. The HCS370 operates over a wide voltage range of 2.05V to 5.5V and has four button inputs in an 14-pin configuration. This allows the system designer the freedom to utilize up to 15 functions.