FlexCAN bit timing calculation

[#1]

This document gives a basic insight into bit timings relationship and provide easy step-by-step guide to calculate CAN bit timing parameters for desired baudrate.

[vrushalitaklika]

Hi Petr,

In the flexcan bit timing calculation,

How do I get the info on these parameters for MPC5777C

STEP 1: Determine minimum permissible time for the PROP_SEG segment. Obtain the maximum propagation delay of the physical interface for both the transmitter and the receiver from the manufacturers data sheet. Calculate the propagation delay of the bus by multiplying the maximum length of the bus by the signal propagation delay of the bus cable. Use these values to calculate tPROP_SEG using equation tPROP_SEG = 2(tBUS + tTX + tRX)

3 Example

Calculate the bit segments for the following system constraints:

 Bit rate = 500k bit per second

 Bus length = 10m

 Bus propagation delay = 5 x 10-9 s/m

 Physical Interface (PCA82C250) transmitter plus receiver propagation delay = 150ns at 85C

 CPI_clock = 40 MHz STEP 1: Physical delay of bus = 10m x 5 ns/m = 50ns tPROP_SEG = 2(50 + 150) = 400 ns

I verified in datasheet, but there is no such mention on propogation delay.

Thanks

vrushali