Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 254)

API Library of Routines
Appendix B
TAG_LOCK
B-123
This function locks the requested TAG memory area.
C Syntax
#include <copro.h>
unsigned TAG_LOCK (tag,timeout)
unsigned tag;
or
char *tag;
unsigned timeout;
Parameters
tag
Use to access the TAG table. This can be either the symbolic TAG or
the handle returned from a TAG_LINK or TAG_DEFINE call.
timeout
Timeout value in seconds, from 0 to 16,383. A value of CC_FOREVER
(defined in COPRO.H) will wait until the TAG has been locked.
Returns
Value Symbolic Name Meaning
0 CC_SUCCESS Operation successful
120 CC_E_BADID TAG define ID out of range
160 CC_E_INV_TO Invalid timeout value
171 CC_E_TIME_LOCKED Did not complete in time, TAG locked
176 CC_E_NOTAG TAG not found
Description
Use the TAG_LOCK function to protect against concurrent access to the
tagged data when accessing the TAG without using TAG_READ or
TAG_WRITE.
Important: After access to the TAG is completed, you must call
TAG_UNLOCK to unlock the TAG; otherwise, the system may hang.
A status of CC_SUCCESS indicates that the calling procedure has locked
the TAG.
TAG_LOCK