Microsecond Bus (μSB): The New Open-Market Peripheral Serial Communication Standard

For the past approximately 20 years, the Serial Peripheral Interface (SPI) has been the established standard for serial communication between a host or central microprocessor and peripheral devices. This standard has been used extensively in control modules covering the entire spectrum of automotive applications, as well as non-automotive applications. As the complexity of engine control modules grows, with the number of vehicle actuators being controlled and monitored increasing, the number of loads the central microprocessor has to manage is growing accordingly. These loads are typically controlled using discrete and pulse-width modulated (PWM) outputs from the microcontroller when real-time operation is essential or via SPI when real-time response is not critical. The increase of already high pin-count on microcontrollers, the associated routing effort and demand for connected power stages is a concern of cost and reliability for future ECU designs. Commonly used methods such as daisy-chaining peripheral devices via SPI or using an SPI bus with a chip-addressing scheme to reduce the number of chip select signals required offer at best an incremental improvement to system capability and do not sufficiently support higher integration of power stages nor common chip set approaches across platforms. These challenges have been addressed with the definition of the new microsecond bus (μSB) interface standard, where implementations are already available with leading microcontroller architectures and a peripheral low-side driver device¹.