What is bit timing?

Bit timing is the count of time Quanta(tq,a basic unit of bit time) required to carry a single bit(i.e tour of a bit on CAN bus from writing to reading) on CAN Bus. reciprocal of Bit timing is known as Bit rate or Nominal bit rate. As per CAN standard CAN supports bit-rate up to 1000 kbps.

CAN bit timing register?

Bit Timing Register Calculation Most CAN controllers allows the programmer to set the bit timing using the following parameters: A clock prescaler value. The number of quanta before the sampling point. The number of quanta after the sampling point.

CAN bit timing tolerance?

The bit timing for each node in a CAN system is derived from the reference frequency (fOSC) of its node. The CAN specification indicates that the worst case oscillator tolerance is 1.58% and is only suitable for low bit rates (125 kb/s or less).

CAN Baudrate calculation?

The following formulas take this into account. So, for this example, a BTR value of 0x1C09 gives a CAN baudrate of 125 kBit/second . But again, the BTR value depends on the clock frequency of the CAN controller ! 8e6 / ( ( 9+1) * ( 3 + 12 + 1 ) = 50000 = 50 kBit/second !

Where does the can bit time come from?

CAN Bit Time derive from Crystal Oscillator. The NBT = 1/NBR. Where, NBT is Nominal Bit Time, and NBR is Nominal Bit or baud Rate. Once you will get the bit time from the bit or baud rate, it will be used to calculate how many number of time quanta required. The CAN bit time is a combination of 4 segments such as:

How is bit timing handled in a CAN network?

In order to assure that all receivers in a CAN network read the transmitted frames correctly they are also required to continuously resynchronize the internal time base with the received bit stream. This is accomplished by continuously adjusting the bit sample point during each bit time.

How to calculate the can bit time for a CAN bus?

Synchronization Jump Width (SJW) in the number of Time Quanta: This is the maximum time that can be used to lengthen or shorten the CAN bit time if there is any change of bit time in between the Transmitter and Receiver ECU. How to Calculate the CAN bit time for a CAN bus

Why do you need time quanta for can bit calculation?

To ensure the zero error in CAN network, the Time quanta is required for CAN bit time calculation. So the time quanta are nothing but the smallest time value for a CAN controller which can be used to increase or decrease the time value of a bit time for soft synchronization or re-synchronization.