The task object corresponding to the Cascade Historian. See locate_task in the Gamma manual.
The name of the history to be described.
A list containing the objects described below if successful. Otherwise returns nil and sets _last_error_ to the error string returned by the Cascade Historian.
This command returns a summary of the configuration parameters associated with the specified history.
The object list returned contains the following (in the given order):
The histname as previously set with the history command, or the HI_History function.
The directory, basename, extension and ndigits as previously set with the filebase command, or the HI_FileBase function.
The full_filename indicates the pathname of the current file to which the data will be written, as set up by the four filebase parameters mentioned above.
The flags are given in hexadecimal format (ie. 0x0064). The following constants define the individual flag bits and may be used to test the flags value:
| Constant | Comment |
|---|---|
| HIST_DISABLED | Indicates history logging state. |
| HIST_REGISTERED | Indicates history is registered with the Cascade DataHub for value updates. |
| HIST_DEADBAND | Overall deadband state (on/off) |
| HIST_DEADBAND_FORCE | Internal state bit. |
| HIST_DEADBAND_PRIOR | Indicates PRIOR mode is set. |
| HIST_DEADBAND_PERCENT | Indicates PERCENT deadband is set. |
| HIST_DEADBAND_ABSOLUTE | Indicates ABSOLUTE deadband is set. |
| HIST_DEADBAND_TIMELIMIT | Indicates TIMELIMIT deadband is set. |
| HIST_DEADBAND_COUNTLIMIT | Indicates COUNTLIMIT deadband is set. |
| HIST_DEADBAND_TYPES | Bit-OR of the deadband type flags (PERCENT, ABSOLUTE, TIMELIMIT, and COUNTLIMIT, useful for testing if any deadband type is set. |
The status of the deadband, t (indicating on) or nil (indicating off). The deadband command (or HI_Deadband API function or hist_deadband DLL function) should be used to determine the actual deadband configuration.
The maxvalues as previously set with the bufsize command, or the HI_Bufsize function.
The point associated with the history, as previously set with the history command, or the HI_History function.
This function corresponds to the describe command, and the Cogent API function HI_Describe.
Gamma> d = hist_describe(tsk, "p3");
("./data" "p3_" ".dat" 2 "./data/p3_01.dat" 0x102 nil 100 "p3")
Gamma> abs_on = (HIST_DEADBAND_ABSOLUTE == (HIST_DEADBAND_ABSOLUTE & car(nth_cdr(d,5))));
t