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How improved data rate and Extended user data benefits CAN FD?

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Improved data rate

Receivers have acknowledged messages, often used in classic CAN, where a wide range of advantages are offered to confirm the transmission’s success rate within the message transmitted with potential transmission errors that can be detected quickly and the data can be re-transmitted quickly enough.

CAN identifier where arbitration of the messages is possible offers an advantage for application control to avoid collisions during transmission of data and short-latency time to be provided for high-priority messages that are even at higher busloads.

The data rate has been significantly increased without the existing communication technology to be changed, CAN FD works with two different bit rates. The control commands with “arbitration rate” that includes arbitration, message type, end detection, and acknowledgment are dependent on the propagation speed led to the network extension.

Also, a second “data bit rate” is often used as an optional method for the data content and security. The achievable data rate is maximum and is dependent on the transmission characteristics of the transmission medium and not the signal propagation.

CAN FD networks enable the current production rate with the use of 8Mbit/s whereby the CAN FD standard is permitted up to 15Mbit/s? In various test systems, the bit rate has been successful where the two data rates are independently set from one another in the CAN FD controller by using two-bit timing registers.

The two data rates can be performed by a switching method to be used by two control bits in the protocol. Till now, the first bit is reserved that can be used as the “Extended Data Length” bit where CAN FD is defined as messages due to its recessive level.

Extended user data

By using well-known lower bit rates, the control data are transmitted where the achievable data rates can be limited. The data area can be increased by up to 64 bytes wherein transfer mode, more amount of data can be sent whereby the increasing data rate can be effective.

As the classic CAN provides only 8 data bytes that no longer is sufficient for many data applications like for transmitting high-precision analog values or a multi-axle robot can be controlled with encoding values that are diverse and with drive commands. This can be perfectly done by adding service data that significantly reduced the effectiveness due to transport protocols where transmission of more than 8 bytes is required.

The option for CAN FD is now provided up to 64 data bytes. In doing so, in a single message, large data blocks are transmitted mainly in-process data cases where more complex devices are controlled completely by using a single process message.

The transport protocol is a necessity for service data where only a single CAN FD message is required only for configuring data and similar. The control data can be prevented from being unnecessarily extended where CAN FD uses only 4bits as a data length code where the value is in the range from 0 to 8 which is taken directly from classic CAN.

Source:- Data rate

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