PROFIBUS Manual

Global control telegram formats

Global control telegram formats

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Global control telegram formats

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The Global_Control telegram consists of two bytes. It is sent by the class 1 master as a multicast to address 127  (0x7F) and SAP = 58 (0x3A). The SDN service is used for this purpose.

 

Global Control:

Control

Group allocation

 

 

7

6

5

4

3

2

1

0

Control

0

0

 

 

 

 

 

0

Reserved

 

 

 

 

 

 

x

 

Clear Data, signalling the operating state of the class 1 master

 

 

 

 

 

x

 

 

UNFREEZE

 

 

 

 

x

 

 

 

FREEZE

 

 

 

x

 

 

 

 

UNSYNC

 

 

x

 

 

 

 

 

SYNC

 

 

7

6

5

4

3

2

1

0

Group allocation

 

 

 

 

 

 

 

x

Group 1

 

 

 

 

 

 

x

 

Group 2

 

 

 

 

 

x

 

 

Group 3

 

 

 

 

x

 

 

 

Group 4

 

 

 

x

 

 

 

 

Group 5

 

 

x

 

 

 

 

 

Group 6

 

x

 

 

 

 

 

 

Group 7

x

 

 

 

 

 

 

 

Group 8 or isochronous clock

 

If the class 1 master is working with an isochronous cycle, group 8 will have a fixed reservation for the clock telegram and can no longer be used freely .