Background

SENT (Single Edge Nibble Transmission), SAE standard J2716, is a one way, point-to-point protocol for transmission of signal values from sensors to a controller. It is used mainly in automotive applications and enables reliable transmission of high-resolution data with lower cost than standards such as CAN, and higher bit rate than LIN.

Data is transmitted in units of 4 bits (1 nibble), for which the time is measured between falling edges (single edge) of the modulated signal. Primary data is normally transmitted in what is called the “Fast channel” with the option to simultaneously send secondary data in the “Slow channel.”

Fast channel transmission typically has two 12-bit data words transmitted in each message frame, although other options are also possible, such as 16 bits for signal 1 and 8 bits for signal 2.

Slow channel data is sent two bits at a time within the standard SENT message frame. So for each fast channel message frame the transmitter can also include two bits of slow channel data: bit 3 and bit 2 of the status nibble. The purpose of the slow channel feature is to allow up to 32 slow channel messages per serial message cycle to be transmitted with minimal impact on the primary sensor data. Slow channel messages can be used to continually monitor information such as temperature, diagnostics and production codes, which either do not change or change at a slower rate than the primary sensor data.

SENT data format is determined by what is best suited to the application. Once the format and data set have been selected, it is usually fixed in the design or configured with nonvolatile memory so that the data is continually transmitted on power up.