The HCS201 is a code hopping encoder designed for secure Remote Keyless Entry (RKE) systems. The HCS201 utilizes Microchip’s patented KEELOQ® code 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 HCS201 combines a 32-bit hopping code generated by a non-linear encryption algorithm, with a 28-bit serial number and 6 status bits to create a 66-bit transmission steam. 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 encryption key, serial number, and configuration data are stored in EEPROM, which is not accessible via any external connection. This makes the HCS201 a very secure unit. The HCS201 provides an easy-to-use serial interface for programming the necessary security keys, system parameters, and configuration data. The encryption key and code combinations are programmable but read-protected. The HCS201 operates over a wide voltage range of 3.5V to 13V and has three button inputs in an 8-pin configuration, which allows the system designer the freedom to utilize up to 7 functions.