ESD CAN - PCC, Hardware Manual

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CAN-PCC Software Manual Rev. 1.4 12
5.1.3 CANPCC_inibit
Like
CANPC_initialize_chip
this function defines the bit timing of the CAN controller. Here,
however, the bitrate is set by transmitting an index value of 0...15 or by transmitting the parameters
btr0
and
brt1
.
Only this function sets a bitrate on the module. Before that the controller does not operate on the CAN!
The typical line lengths specified below are based on facts from experience. The minimum reachable
line lengths result from the 'worst case' delay times of the components used.
index
87C592-register
Bitrate
[kbit/s]
typical values of minimum
reachable line reachable line
lengths l [m] lengthn l [m]
max min
btr0 btr1
[HEX] [HEX]
0 00 14 1000 37 20
1 00 18 666.6 80 65
2 00 1C 500 130 110
3 01 18 333.3 180 160
4 01 1C 250 270 250
5 02 1C 166 420 400
6 03 1C 125 570 550
7 04 1C 100 710 700
8 45 2F 66.6 1000 980
9 09 1C 50 1400 1400
10 4B 2F 33.3 2000 2000
11 18 1C 20 3600 3600
12 5F 2F 12.5 5400 5400
13 31 1C 10 7300 7300
14 00 16 800 59 42
The specifications in the table are based on the limit values of the bit timing of the CAN protocol, the delay times of
the local CAN interface and the delay times of the cable. The delay time of the cable is assumed at about 5.5 ns/m.
Further influences, as for instance caused by missing terminators, the specific resistance, the cable geometry or
external disturbances during transmission, have not been considered in the specifications!
Table 5.1.2: Parameters
index
,
btr0
and
btr1
for setting the bitrate