PROFIBUS DP-Master

Overview 80/315
The length of the complete check configuration data block must not exceed 244 bytes, however, it is
recommended not to exceed an amount of 32 bytes otherwise some restrictions apply, see the
underlying IEC 61158 or EN 50170 specification.
5.3.3.2 Identifier Byte for the General Format
The identifier byte can be specified in the general (also called compact) format or the special format.
In the general format, the meaning of the single bits is defined as follows:
General Identifier Format of Identifier Byte
(according to IEC 61158/EN 50170 Specification)
Bit Name Value Description
D7 Consistency Consistency extends over
0 Byte or word (in case of D6 = 0)
1 Whole length (in case of D6 = 1)
D6 Length format Length format
0 Byte structure
1 Word structure
D5 Output
Input/Output/Special identifier format
0 D4=0 This combination signifies the special
identifier format, see below.
D4=1 Input
1 D4=0 Output
D4=1 Input- Output
D4 Input See above (D5). D5 and D4 are evaluated together.
D3 Length of data 0 1 Byte/Word
1
…
15 16 Bytes/Words
(choice of byte or word depends on length format bit)
Table 38: General Identifier Format of Identifier Byte according to IEC 61158/EN 50170 Specification
Note: When transferring data in word mode, the high byte is transferred first by Profibus DP,
then the low-byte. However, the Profibus DP Master has the possibility to swap this sequence
of the bytes within the word, if required by the target system.
5.3.3.3 Identifier Byte for the Special Format
To allow extended configurations and to increase flexibility, a special extension of the identifier system
described above is also supported by Profibus DP. The main advantages of this format are:
• It is possible to determine the number of input and output bytes associated to the defined
identifier.
• User specific data can be added.
PROFIBUS DP-Master |
DOC061001API12EN | Revision 12 | English | 2010-12 | Released | Public © Hilscher, 2006-2010