Agilent Technologies TwisTorr 84 FS AG Mode D'emploi page 284

17 Technical Information
Profibus Option
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:
So, if the first byte is equal to 0, the interface is working
properly, otherwise there is a problem.
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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)
TwisTorr 84 FS AG Rack Controller User Manual / 87-901-037-01 (A)