PROFIBUS-DP field bus
PCD0
26/766 E2
(HB_PCD0 26 766_E2.DOC)
SAIA-Burgess Controls Ltd.
Page 177
13.10
PROFIBUS-DP response times
The response time is defined as the total time of a message cycle
between the master and an individual slave.
A message cycle consists of a request telegram to the slave,
mandatory bus idle times and the response time of the slave.
The bus cycle time is the total of all the message cycles.
To calculate the response time:
12Mbaud
28µs + 1µs/data byte to be transmitted
1.5Mbaud
224µs + 7µs/data byte to be transmitted
Example:
10 bus nodes with 8 bytes of output data and 8 bytes of input data
each
12Mbaud:
28 + 8 + 8 = 44µs
Response time
44 * 10 = 440µs
Bus cycle time
1.5Mbaud:
224 + (7*8) + (7*8) = 336µs
Response time
336 * 10 = 3.4ms
Bus cycle time
Add a manufacturer-specific run time in the DP master (typically 1 -
3ms).
Therefore the duration of a bus cycle in which all slaves are contacted
once is approx. 2 - 4ms at 12Mbaud.
