The 68HC05**** (also abbreviated as HC05) is a broad family of 8-bit microcontrollers from Motorola Semiconductor (later Freescale then NXP). Like all Motorola processors that share lineage from the 6800, they use the von Neumann architecture as well as memory-mapped I/O. This family has five CPU registers that are not part of the memory: an 8-bit accumulator A, an 8-bit index register X, an 8-bit stack pointer SP with two most significant bits hardwired to 1, a 13-bit program counter PC, and an 8-bit condition code register CCR. Among the HC05's there are several processor families, each targeted to different embedded applications. The 68HC05 family broke ground with the introduction of the EEPROM-based MC68HC805C4 and MC68HC805B6 variants in the late 1980s. Using a serial bootloader, they could be programmed in-circuit with simple software running on a PC and a low current 19 V supply (no programmer required). The HC05 series is now considered legacy and is replaced by the HC(S)08 MCU series.

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