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. One 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 1980's. Using a serial bootloader, they could be programmed in-circuit with simple software running on a PC and a low current 19V supply (no programmer required).
The HC05 series is now considered legacy and is replaced by the HC(S)08 MCU series.
- 68HC05 Processor Families
- Archives of old 68HC05 and 68HC705 manuals
- Digital Core Design 68HC05 - HDL IP Core
- MC68HC805B6 (6k EEPROM program memory) Programmer
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