Hi everyone

i have a few questions regarding profibus. what is exact number of devices i can connect in a profibus dp network.

generally i have read about 126 but the manual states that i can connect max 127.

so can any one explain it clearly.(total devices including 1 master and rest slaves)

and next question is what can be maximum masters in a network?

Ashwin pandey

hi ashwin,

in a Profibus-network you need at least one master, so you can have only 126 slaves with one master = 127 nodes

hope this helps,

regards,

Hello,

Fritz wrote:

124 (not 125) DP Slaves is (should be) the maximum number of DP Slaves per DP Master interface of an S7.
Reason being is that S7 HWconfig will (for good reasons) warn you if you try to use 0 as the DP Masters address (typically used by a PG, but also required to be free if routing is used), so Address 1 is the lowest possible useable address in a DP Network and 125 is as always the highest one.
This totals to 125, minus one address for the DP Master makes for a practical maximum of 124 DP Slaves.
Having said that, some other DP Masters do (rather unfortunately) allow usage of 0 as the lowest address in which case 125 DP Slaves can be used on them.

and another info from fritz:

Max Address Settable in Profibus DP - Entries - Forum - Industry ...

Ste39

Hello,

Fritz wrote:

124 (not 125) DP Slaves is (should be) the maximum number of DP Slaves per DP Master interface of an S7.
Reason being is that S7 HWconfig will (for good reasons) warn you if you try to use 0 as the DP Masters address (typically used by a PG, but also required to be free if routing is used), so Address 1 is the lowest possible useable address in a DP Network and 125 is as always the highest one.
This totals to 125, minus one address for the DP Master makes for a practical maximum of 124 DP Slaves.
Having said that, some other DP Masters do (rather unfortunately) allow usage of 0 as the lowest address in which case 125 DP Slaves can be used on them.

and another info from fritz:

Max Address Settable in Profibus DP - Entries - Forum - Industry ...

Hello

Thanks for replying.

but my set PG/PC setting is showing address from 1 to 126. and 0 is address of PG/PC so total devices must be 126. 1 master and 125 slaves

ashwin pandey

 

Ste39

Hello,

Fritz wrote:

124 (not 125) DP Slaves is (should be) the maximum number of DP Slaves per DP Master interface of an S7.
Reason being is that S7 HWconfig will (for good reasons) warn you if you try to use 0 as the DP Masters address (typically used by a PG, but also required to be free if routing is used), so Address 1 is the lowest possible useable address in a DP Network and 125 is as always the highest one.
This totals to 125, minus one address for the DP Master makes for a practical maximum of 124 DP Slaves.
Having said that, some other DP Masters do (rather unfortunately) allow usage of 0 as the lowest address in which case 125 DP Slaves can be used on them.

and another info from fritz:

Max Address Settable in Profibus DP - Entries - Forum - Industry ...

Hello

Thanks for replying.

but my set PG/PC setting is showing address from 1 to 126. and 0 is address of PG/PC so total devices must be 126. 1 master and 125 slaves

 Dear aswin,

please have a look in particular at page 16 :

PROFIBUS Design and good practices