CHARMs support the same type of failure action operation as I/O cards. When the CIOC is downloaded, a two second time out period is enabled in the CHARMs. If communications to the CIOC are lost for more than two seconds, the CHARMs will enter the failure action mode. This two second timeout period is not configurable by the user, nor can it be disabled. In addition, if the CIOC loses communications with a controller for three seconds, all output CHARMs assigned to that controller will enter the failure action mode.
A CHARM's failure action operation depends upon its type. All configured CHARMs turn on the red Error LED, but only output CHARMs take any further failure action. The following failure action configuration options are available for configured OUTPUT CHARMs:
Failure Action Mode – Designates if the CHARM should HOLD LAST VALUE or OUTPUT FAILURE ACTION VALUE.
Failure Action Value – Specifies the value used if the CHARM is configured to OUTPUT FAILURE ACTION VALUE.
| Card | Failure Action Mode options |
|---|---|
|
Analog Output |
Hold Last Value: The output is held at the last value received from the controller before the failure action condition occurred. Go to Configured Failure Action: The output is driven to the configured failure action value when the failure action condition is entered. Note All outputs values below 1 mA (including failure action values) are clamped to 1mA to ensure that the open loop detection mechanism of the D/A converter is always operable. |
|
Discrete Output |
Hold Last Value: The outputs continue with the latest configuration and output values. This applies to all CHARM types. If the CHARM is configured to be continuous pulse output type, it continues with the latest period and duty cycle. If it is configured to be a momentary pulse output type, it continues to process the current pulse. No additional pulses can be generated. Go to Configured Failure Action: In this mode, failure action forces the outputs to go to predefined levels. If the CHARM is configured as momentary or continuous pulse output type, the pulse is aborted for the failure action value. |