Rockwell Automation 1756-L7x GuardLogix 5570 Controllers - Manual (Page 122)

122 Rockwell Automation Publication 1756-UM022A-EN-P - November 2012
Chapter 9 Monitor Status and Handle Faults
Use GSV/SSV Instructions
Logix controllers store system data in objects rather than in status files. You can
use the Get System Value (GSV) and Set System Value (SSV) instructions to
retrieve and set controller data.
The GSV instruction retrieves the specified information and places it in the
specified destination. The SSV instruction changes the specified attribute with
data from the source of the instruction. When you enter a GSV or SSV
instruction, the programming software displays the object classes, object names,
and attribute names for each instruction.
For standard tasks, you can use the GSV instruction to get values for the available
attributes. When using the SSV instruction, the software displays only those
attributes you are allowed to set.
For the safety task, the GSV and SSV instructions are more restricted. Note that
SSV instructions in safety and standard tasks cannot set bit 0 (major fault on
error) in the mode attribute of a Safety I/O module.
For safety objects, the Table 41 shows which attributes you can get values for by
using the GSV instruction, and which attributes you are allowed to set by using
the SSV instruction, in the safety and standard tasks.
ATTENTION: Use the GSV/SSV instructions carefully. Making changes to
objects can cause unexpected controller operation or injury to personnel.
Table 41 - GSV/SSV Accessibility
Safety
Object
Attribute Name Data Type Attribute Description
Accessible from
the Safety Task
Accessible from
Standard Tasks
GSV SSV GSV
(4)
SSV
Safety Task
Instance DINT Provides instance number of this task object. Valid values are
0…31. ✓ ✓
MaximumInterval DINT[2] The max time interval between successive executions of this task. ✓ ✓
MaximumScanTime DINT Max recorded execution time (ms) for this task. ✓ ✓
MinimumInterval DINT[2] The min time interval between successive executions of this task. ✓ ✓
Priority INT Relative priority of this task as compared to other tasks. Valid
values are 0…15. ✓ ✓
Rate DINT Period for the task (in ms), or timeout value for the task (in ms). ✓ ✓
Watchdog DINT Time limit (in ms) for execution of all programs associated with this
task. ✓ ✓
Safety
Program
Instance DINT Provides the instance number of the program object. ✓ ✓
MajorFaultRecord (1) DINT[11] Records major faults for this program. ✓ ✓ ✓
MaximumScanTime DINT Max recorded execution time (ms) for this program. ✓ ✓
Safety
Routine Instance DINT Provides the instance number for this routine object. Valid values
are 0…65,535. ✓