CAN Bit Segmentation — Bit Monitoring and Bit Segments

Bit Monitoring

Bit Monitoring — Bit SamplePoint

• Bit Monitoring: This process involves nodes monitoring the bus for the current bit value.
• Sampling: Nodes sample the bus voltage value to determine the current bit’s value, a process that occurs for each bit.
• Transmission (Tx) Nodes: These nodes first place the bit value on the bus and then monitor whether the bus has properly taken that value.
• Reception (Rx) Nodes: These nodes sample the bus to read the bit value.
• In the provided image, each arrow represents the point at which bit sampling occurs, corresponding to the various square waves, each representing one bit.
• There are a total of 9 bits depicted in the image.
• These arrows indicate the specific times when bit sampling occurs, allowing nodes to determine the bit value as logic 1 or logic 0 based on the bus’s state.
• Sampling can occur at any part of the particular bit, and the specific timing of sampling within a bit can be better understood after understanding the bit segments.

To understand this concept better, we need to delve into the concept of bit segments.

What are Bit Segments?

Each CAN bit is divided into four segments:

• Synchronization Segment
• Propagation Segment
• Phase Segment 1
• Phase Segment 2

Bit Segments

• The intersection of Phase Segment 1 and Phase Segment 2 is where bit sampling occurs, known as the bit sample point.
• These four bit segments are present in every single bit.
• The size of these segments varies, but the sum of all segments equals the total bit time.
• The total of these segments will always be equal to the bit time for each bit.

In the upcoming section, we will explore each of these segments in detail to understand their roles and functions in the CAN protocol.