3.3 Special signals
In some cases, it is useful/necessary to access the status or configuration variables of the driver. The signals below marked with the R (W) letter are readable (writeable) signals, i.e. they are inputs (outputs) of the control system.
The driver performs these special signals:
_DGNRESET | W | reset of the accumulated diagnostics information |
_TRANSACTIONS | R | total number of transactions with owserver |
_RECONNECTS | R | number of reconnections (after communication errors) |
All global signals starts with the _ (underscore) character. In these cases the tripple underscore will be used (e.g. OWS___DGNRESET) because of the __ (double underscore) separator between the diver tag and the signal name.
Moreover, each signal can be suffixed with a special text which determines that a special attribute of the signal will be used instead of the signal value. The special suffixes are the following (all begins with _):
_Value | RW | alias for signal value |
_DGNRESET | W | reset of the diagnostics information for the given signal |
_TRANSACTIONS | R | number of transactions with owserver for the given signal |
_ReadEnable | RW | enable to read the signal; equivalent: _RE |
_WriteEnable | RW | enable to write the signal; equivalent: _WE |
_WriteOneShot | W | one-shot write of the signal; equivalent: _WOS |
_Alarm | R | alarm flag of the signal; after reading it is cleared |
_PerFactor | R | driver period multiplier for the signal update |
_PerCount | R | number of the driver periods from the last signal update |
_PerMax | R | maximum number of the driver periods between two consecutive signal updates |
_PendCount | R | current number of waiting cycles for returning the value from owserver |
_PendLast | R | last number of waiting cycles for returning the value from owserver |
_PendMax | R | maximum number of waiting cycles for returning the value from owserver |
_Period | R | update period (in seconds) of the signal |
_Age | R | the time elapsed since the last update of the signal (signal age) |
_AgeMax | R | maximum signal age from the last reset of the diagnostics information |
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