Safe State Value
You can select specific values for your analog output or input/output Combo module to maintain in the event of a network communication error, or when the controller enters the Program mode. This is known as a "Safe State".
In order to fully understand how Safe State is applied during a communication fault, you must set either the Communication Fault Behavior or the Program Mode Behavior to "Apply Safe State to Outputs" from the Fault/Idle Action tab on the Module Properties dialog box. Communication Fault Behavior and Program Mode Behavior are discussed below.
Communication Fault Behavior
This module feature determines how module alarm outputs react to communications between the modules in the system and internal module faults. From the Fault/Idle Action tab, Module Properties dialog box, choose the way in which you want the adapter to respond when a communication fault occurs with this module. Upon detection of a communication fault, modules can be set to:
- Reset Outputs- Returns the module output data to zero.
- Hold Last Outputs- Retains the module output data in its last state.TIP:If you select this option, you cannot select Apply Safe State to Outputs in the Program Mode Behavior field below.
- Apply Safe State to Outputs- Makes the safe state values effective to the module output.TIP:If you select this option, you cannot select Hold Last Outputs in the Program Mode Behavior field discussed below.
Program Mode Behavior
This module feature allows you to select the way in which you want the adapter to respond when it detects Program mode (idle). This is the controller mode during which logic is not executing, I/O is not controlled, and editing operations are available. The adapter detects the state of the controller or scanner. There are only two states it detects: Run mode and Program mode. When it detects Run mode, the adapter copies the output data from the controller to the corresponding module output. When it detects Program mode, it responds according to the choice you select for this field. Program Mode Behavior is selected from the Fault/Idle Action tab, Module Properties dialog box. There are three choices:
- Reset Outputs- Returns the module output data to zero.
- Hold Last Outputs- Retains the module output data in its last state.TIP:If you select this option, you cannot select Apply Safe State to Outputs in the Communication Fault Behavior field above.
- Apply Safe State to Outputs- Makes the safe state values effective to the module output.TIP:If you select this option, you cannot select Hold Last Outputs in the Communication Fault Behavior field discussed above.
When you click the Apply button from the Fault/Idle Action tab, validation of the Safe State value occurs. (The Voltage/Current Range specified on the Configuration tab determines the valid ranges). If you specify a value that is out of range, an error message displays with the correct range to use.
Safe State for FLEX I/O Analog Output Modules
The following table lists the valid Safe State value, which is based on the setting you use on the Output Configuration tab in the Voltage/Current Range field for FLEX I/O analog modules. Choose from the list of modules following this table for those modules that are exceptions.
Output Configuration Tab Voltage/Current Range Field | Safe State Value (Decimal) |
None | 0 |
4 to 20 mA - Signed Two’s Complement | -32768 - 32767 |
-10 to 10 V - Signed Two’s Complement | -32768 - 32767 |
-5 to 5 V - Signed Two’s Complement | -32768 - 32767 |
0 to 20 mA - Signed Two's Complement % | 0 - 10500 |
4 to 20 mA - Signed Two's Complement % | -2500 - 10500 |
0 to 10V - Signed Two's Complement % | 0 - 10500 |
-10 to 10V - Signed Two's Complement % | -10500 - 10500 |
-20 to 20 mA - Offset Binary | 32768 - 65535 |
All others | 0-65535 |
Safe State Value Range Exceptions
Safe State values vary among FLEX I/O analog output modules. Choose the desired module from the list of modules below for their Safe State values.
Input | Output |
Safe State for Digital Modules
The safe state for digital modules is slightly different than it is for analog modules. For digital modules, the outputs are automatically set to On or Off when you choose the
Apply Safe State to Outputs
for the Communication Fault or Program mode behavior.
TIP:
In order to use this feature, you must set the Communication Fault Behavior or the Program Mode Behavior to "Apply Safe State to Outputs" as discussed above.
Safe State Value Ranges for FLEX I/O Combo Modules
Safe State values vary among FLEX I/O Combo modules. Choose the desired module from the list of Combo modules below for their Safe State values.
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