Capacity Planning Of The System Bus - BONFIGLIOLI Active Cube User Manual

7.14.3

Capacity planning of the system bus

Each PDO telegram possesses a constant useful data content of 8 Bytes. According to
worst case, this results in a maximum telegram length of 140 bits. The maximum
telegram run time of the PDOs is thus stipulated via the set baud rate.
As a function of the set baud rate and the transmission interval of the TxPDOs se-
lected, the following bus loads results:
Baud
rate /
kBaud
1.000
500
250
125
100
50
Atten-
tion:
This observation must be done for each TxPDO. The sum of all the TxPDOs decides
on the entire bus load. The bus load must be designed in such a way that any tele-
gram repetitions for transmission errors are possible without exceeding the bus ca-
pacity.
Note:
82
Capacity planning
Baud rate Telegram runtime
kBaud
1000
500
250
125
100
50
Capacity of the system bus
Bus load as a function of the transmission for one TxPDO in %
1ms 2ms 3ms 4ms
14 7 4,7
28 14 9,3
56 28 18,7
112 56 37,3
140 70 46,7
280 140 93,3
A bus load >100% means that a telegram cannot be dispatched com-
pletely between two transmission times.
Such a setting is not admissible!
To facilitate capacity planning, a Microsoft Excel file with the name
"Load_Systembus.xls" is available.
EM-ABS-01 for ACU
μs
140
280
560
1120
1400
2800
5ms 6ms 7ms
3,5 2,8 2,3
7 5,6 4,7
14 11,2 9,3
28 22,4 18,7 16
35 28 23,3 20
70 56 46,7 40
8ms 9ms 10ms
2 1,8 1,6 1,4
4 3,5 3,1 2,8
8 7 6,2 5,6
14 12,4 11,2
17,5 15,6 14
35 31,1 28
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