PROFIBUS Manual

Length information

Length information

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Length information

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The two equivalent length bytes in the telegram header of the variable format contain the number of information bytes in the body of the telegram. These include: DA, SA, FC and the PDU. The value ranges from 4 to 249, so that no more than 246 bytes can be transferred to the PDU of a telegram. No value <4 is allowed, because a telegram must comprise at least one DA, SA ,FC and a data byte. The longest telegram therefore comprises 255 bytes overall.

 

7

6

5

4

3

2

1

0

LE and LEr: length byte

4  to 249

Length byte