What is the difference between CAN 2.0A and CAN 2.0B?

The Controller Area Network (CAN) protocol has been widely used in various industries for communication between electronic devices. Two common variants of the CAN protocol are CAN 2.0A and CAN 2.0B. Although they are similar, there are several key differences that set them apart. This article aims to provide an easy-to-understand explanation of the dissimilarities between CAN 2.0A and CAN 2.0B.

CAN 2.0A: Standard format

CAN 2.0A, also known as the Standard or Base format, defines a message frame with an 11-bit identifier. This means that a CAN 2.0A frame can have up to 2^11 (2048) unique message identifiers. It uses Non-Return to Zero (NRZ) bit encoding and supports a maximum data rate of 1 Mbps. CAN 2.0A is commonly utilized in applications where the network size is relatively small and error detection is crucial. One drawback of CAN 2.0A is its limited identifier space, which may be a constraint for larger-scale systems.

CAN 2.0B: Extended format

CAN 2.0B, also referred to as the Extended format, introduces a longer 29-bit identifier compared to CAN 2.0A. This extended length provides a significantly larger identifier space of up to 2^29 (536,870,912) unique message identifiers. The extended format allows for increased flexibility in assigning unique IDs to nodes in larger networks. With NRZ bit encoding and the same maximum data rate of 1 Mbps as CAN 2.0A, CAN 2.0B is widely used in applications that require a higher number of nodes and a more extensive identifier range.

Differences in error detection and handling

CAN 2.0A adopts a single error detection mechanism called the CRC-15, which allows for error detection on up to five bits in an identifier. On the other hand, CAN 2.0B utilizes a stronger error detection method known as CRC-17, enabling error detection on up to six bits in an identifier. Additionally, CAN 2.0B introduces a new feature called "Error Flag," which can help identify faulty nodes within the network. This enhanced error detection and fault confinement make CAN 2.0B more resilient in larger and more complex systems.