Siemens SIMATIC NET PROFIBUS - Manual (Page 426)

30 Version 1.0 8/00
Configuration 6.2 Configuration of redundant optical rings
Data rate a b c
12 MBit/s 1) 1651 240 28
6 MBit/s 1) 951 120 24
3 MBit/s 1) 551 60 24
1.5 MBit/s 351 30 24
500 kBit/s 251 10 24
187.5 kBit/s 171 3.75 24
93.75 kBit/s 171 1.875 24
45.45 kBit/s 851 0.909 24
19.2 kBit/s 171 0.384 24
9.6 kBit/s 171 0.192 24
Table 3a: Constants for calculating the slot time at DP standard
(redundant optical ring)
Data rate a b c
12 MBit/s 1) 1651 240 28
6 MBit/s 1) 951 120 24
3 MBit/s 1) 551 60 24
1.5 MBit/s 2011 30 24
500 kBit/s 771 10 24
187.5 kBit/s 771 3.75 24
93.75 kBit/s 451 1.875 24
45.45 kBit/s 851 0.909 24
19.2 kBit/s 181 0.384 24
9.6 kBit/s 171 0.192 24
Table 3b: Constants for calculating the slot time at DP/FMS (”universal“)
and DP with S5 95U (redundant optical ring)
The calculation of the slot time only takes into consideration the optical network and the connection of bus sub-
scribers to the OLM via an RS 485 bus segment with a respctive length of max. 20 m. Longer RS 485 bus segments
must be allowed for by adding them to the Length
OF
.
Note:
When the slot time is configured with a too small value the OLM will, through it’s fault function and fault indications,
indicate such. The System-LED will blink red/green.
1) Using the OLM/G11-1300 and OLM/G12-1300 at data rates of 12 MBit/s, 6 MBit/s, 3 MBit/s and 1.5 MBit/s the
minimum slot times according to the following table must be met.
Data rate Minimum slot time
12 MBit/s 3800 t
Bit
6 MBit/s 2000 t
Bit
3 MBit/s 1000 t
Bit
1.5 MBit/s 530 t
Bit
Table 4: Minimum slot time on OLM/G11-1300 and
OLM/G12-1300
Use the values from Table 4 if the calculated slot time is smaller than the minimum slot time indicated in the table.