at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 666

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

Delay of the bus driver: 50 ns
Delay of the receiver: 30ns
Delay of the bus line (20m): 110ns
The total number of time quanta in a bit time must be comprised between 8
and 25. If we fix the bit time to 16 time quanta:
Tcsc = 1 time quanta = bit time / 16 = 125 ns
=> BRP = (Tcsc x MCK) - 1 = 5
The propagation segment time is equal to twice the sum of the signal’s
propagation time on the bus line, the receiver delay and the output driver
delay:
Tprs = 2 * (50+30+110) ns = 380 ns = 3 Tcsc
=> PROPAG = Tprs/Tcsc - 1 = 2
The remaining time for the two phase segments is:
Tphs1 + Tphs2 = bit time - Tcsc - Tprs = (16 - 1 - 3)Tcsc
Tphs1 + Tphs2 = 12 Tcsc
Because this number is even, we choose Tphs2 = Tphs1 (else we would choose
Tphs2 = Tphs1 + Tcsc)
Tphs1 = Tphs2 = (12/2) Tcsc = 6 Tcsc
=> PHASE1 = PHASE2 = Tphs1/Tcsc - 1 = 5
The resynchronization jump width must be comprised between 1 Tcsc and the
minimum of 4 Tcsc and Tphs1. We choose its maximum value:
Tsjw = Min(4 Tcsc,Tphs1) = 4 Tcsc
=> SJW = Tsjw/Tcsc - 1 = 3
Finally: CAN_BR = 0x00053255
AT91SAM9263 Preliminary
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6249D–ATARM–20-Dec-07