Siemens SIMATIC NET PROFIBUS Benutzerhandbuch

3-31

PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000

For the transmission rates of 1.5 Mbps selected in the example, Table 3-9 lists the
following values

a = 351
b = 30
c = 24

On this basis, the slot time is calculated as follows:

Slot time = 351 + (30 x 20) + (24 x 20) = 1431

This means that the following three bus parameters must be entered for the
example:

Slot time (T_slot_Init) 

= 

1431

Retries (Retry_Limit) 

=

      3

Highest station address (HSA)

= 

    126   (default)

These values are entered in STEP 7 in the “Bus Parameters” dialog for the
“User-Defined” bus profile.

You must then trigger the recalculation of the bus parameters with the
“Recalculate” button.