ctTagRead | Extensibility

Reads the value, quality and timestamp, not only a value. The data will be returned in string format and scaled using the Citect SCADA scales.

The function will request the given tag from the Citect SCADA I/O Server. If the tag is in the I/O Servers device cache the data will be returned from the cache. If the tag is not in the device cache then the tag will be read from the I/O Device. The time taken to complete this function will be dependent on the performance of the I/O Device. The calling thread is blocked until the read is completed.

Type: Handle
Input/output: Input
Description: The handle to the CTAPI as returned from ctOpen().

Type: LPCSTR
Input/output: Input
Description: The tag name or tag name and element name, separated by a dot. If the element name is not specified, it will be resolved at runtime as for an unqualified tag reference. You may use the array syntax [] to select an element of an array.

Variable tags can be specified as a string in multiple forms. Refer to Tag Names for more information.

Type: LPCSTR
Input/output: Output
Description: The buffer to store the read data. The data is returned in string format.

Type: Dword
Input/output: Input
Description: The length of the read buffer. If the data is bigger than the dwLength, the function will not succeed.

TRUE if successful, otherwise FALSE. Use GetLastError() to get extended error information.

HANDLE   hCTAPI = ctOpen(NULL, NULL, NULL, 0);

           
char 	sProcessValue[20];
char 	sProcessValueField[20];
char	sProcessValueControlMode[20];
char	sProcessValueStatus[20];
ctTagRead(hCTAPI,"PV123", sProcessValue, sizeof(sProcessValue));
ctTagRead(hCTAPI,"PV123.Field", sProcessValueField, sizeof(sProcessValueField));
ctTagRead(hCTAPI,"PV123.Field.V", sProcessValueField, sizeof(sProcessValueField));
ctTagRead(hCTAPI,"PV123.ControlMode",sProcessValueControlMode, sizeof(sProcessValueControlMode));
ctTagRead(hCTAPI, "PV123.Status", sProcessValueStatus, sizeof(sProcessValueStatus));