Agilent Technologies TV 301-P Navigator Notice De Mode D'emploi page 212

17 Technical Information
Profibus message mapping
In order to don't overload the controller's internal serial link, following
NOTE
precautions are taken:
• The parameters are written from the Profibus gateway to the controller only
when their value changes.
• The parameters are never read back from the controller to the interface. The
controller's response at the write com-mand (ACK, NACK, etc) is used to
establish if the writing succeed or not.
Diagnostic Management
In addition to the ProfiBus six byte standard diagnostic, the interface
provides both user diagnostic and static diagnostics functions
The standard diagnostic management is fully compliant with the
ProfiBus specification.
During the start-up phase after power on, the first byte in the user
diagnostic area, can assume values different from zero.
This byte has the following meaning:
Bit 0 = 1: controller not responds (RS485 link broken)
Bit 1 = 1: controller not identified (not compatible with the
ProfiBus gateway)
Bit 2 = 1: first loop of requests not ended (values in the input data
are not fully coherent yet)
So, if the first byte is equal to 0, the interface is working properly,
otherwise there is a problem.
Each nibble in the bytes following the interface status byte represents
the status of the last attempt to write a parameter with following
coding (diag status byte):
0
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Write success
TV 301-P Navigator Controller User Manual / 87-901-001-01 (B)