I/O System S900
Communication Interface for PROFIBUS DP, CI920
between two diagnostic telegrams (or messages) the S900 ensures that a new
buffer (with changed data) is only handed over to the PROFIBUS after the
master has read the "old" buffer. This prevents that rapidly incoming and
outgoing diagnostic data (e.g. line break signals in case of a loose contact)
will overload the PROFIBUS with diagnostic telegrams.
Structure
The structure of the diagnostic telegram complies with the PROFIBUS DP
standard with extension DPV1. Alarms are not supported. Thus, vendor-
specific diagnostic messages are only possible in the channel-specific
diagnostic part.
Module errors (incl. CI920) are transmitted as diagnostic data for channel 0.
Table 4-6 Diagnostics, overview
0..5 6..14
15..18
19..
Header Status
diagnostics
Identifier-specific
diagnostics
Channel-specific
diagnostics
Header
Octet 1: Station_status_1
The individual bits have the following meaning:
Bit 7
Diag.Master_Lock
The DP slave has been parameterized from another master. This bit is set
by the DP master (Class_1), if the address in octet 4 is different from 255
and different from the own address. The DP slave sets this bit to zero.
Bit 6
Diag.Prm_Fault
This bit is set by the DP slave if the last parameter frame was faulty, e. g.
wrong length, wrong Ident_Number, invalid parameters.
Bit 5
Diag.Invalid_Slave_Response
This bit is set by the DP master as soon as receiving a not plausible
response from an addressed DP slave. The DP slave sets this bit to zero.
Bit 4
Diag.Not_Supported
This bit is set by the DP slave as soon as a function was requested which
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3BDD010422R0101
