The C166 family is a 16-bit microcontroller architecture from Infineon (formerly the semiconductor division of Siemens) in cooperation with STMicroelectronics. It was first released in 1993 and is a controller for measurement and control tasks. It uses the well-established RISC architecture, but features some microcontroller-specific extensions such as bit-addressable memory and an interrupt system optimized for low-latency. When this architecture was introduced the main focus was to replace 8051 controllers (from Intel).
The Siemens/Infineon C167 family or STMicroelectronics ST10 family is a further development of the C166 family. It has improved addressing modes and support for "atomic" instructions. Variants include, for example, Controller Area Network (CAN bus).