Emp­foh­le­nes Bit­ti­ming und Buslänge

Bit­ti­ming as in CiA Draft Stan­dard 102 Ver­si­on 2.0

Bit rate (1)	Bus length	Nomi­nal Bit time	Num­ber of time quan­ta per bit	Loca­ti­on of sample point time quanta	Loca­ti­on of sam­ple point percentage
10 kbit/​s	5000 m (3)	100 µs	16	14	87,5 %
20 kbit/​s	2500 m (3)	50 µs	16	14	87,5 %
50 kbit/​s	1000 m (3)	20 µs	16	14	87,5 %
125 kbit/​s	500 m (2)	8 µs	16	14	87,5 %
250 kbit/​s	250 m (2)	4 µs	16	14	87,5 %
500 kbit/​s	100 m	2 µs	16	14	87,5 %
800 kbit/​s	50 m	1,25 µs	10	8	80 %
1 Mbit/​s	25 m	1 µs	8	6	75 %

Oscil­la­tor fre­quen­cy: 16 MHz +/-0.1% (1000 ppm)
Sam­pling mode: Sin­gle sam­pling SAM = 0
Syn­chro­niza­ti­on mode: Reces­si­ve to domi­nant edges only SYNC = 0
Syn­chro­niza­ti­on jump width: 1 * tq SJW = 0
Pha­se Seg­ment 2: 2 * tq TSEG2 = 1

Note 1: Roun­ded bus length esti­ma­ti­on (worst case) on basis 5 ns/​m pro­pa­ga­ti­on delay and a total effec­ti­ve ECU-inter­nal (Elec. Con­trol Unit) in-out delay as follows:

• 1M-800 kbit/​s: 210ns
• 500 – 250 kbit/​s: 300 ns (includes 2 * 40 ns for optocouplers)
• 124 kbit/​s: 450 ns (includes 2 * 100 ns for optocouplers)
• 50 – 10 kbit/​s: 1.5 tq; Effec­ti­ve delay = delay reces­si­ve to domi­nant plus domi­nant to reces­si­ve divi­ded by two.

Note 2: For bus length grea­ter than about 200 m the use of opto­cou­plers is recom­men­ded. If opto­cou­plers are pla­ced bet­ween CAN con­trol­ler and trans­cei­ver this affects the maxi­mum bus length depen­ding upon the pro­pa­ga­ti­on delay of the optocouplers
i.e. ‑4m per 10 ns pro­pa­ga­ti­on delay of employ­ed opto­cou­pler type.

Note 3: For bus length grea­ter than about 1 km bridge or repea­ter devices may be needed.