1756-RM001B-EN-P, Using ControlLogix in SIL2 ... - Tuv-fs.com

6-8 ControlLogix I/O ModulesGeneral Considerations when using Any ControlLogix DigitalOutput ModuleWiring the two types of digital output modules differs, depending onyour application requirements (these wiring methods are explained indetail in later sections). However, regardless of the type ofControlLogix output module used, there are a number of generalapplication considerations that you must follow when applying thesemodules in a SIL2 application:• Proof Tests - Periodically (for example, once every severalyears) a System Validation test must be performed. Manually, orautomatically, test outputs to make sure that all outputs areoperational and not stuck in the ON or OFF state. Outputs mustbe cycled from ON to OFF or OFF to ON. For additionalinformation on Proof Tests, see page 1-5 and Figure 9.1 onpage 9-5.• Examination of Output Data Echo signal in Applicationlogic: The application logic must examine the Data Echo valueassociated with each output point to make sure that therequested On/Off command from the controller was received bythe module.In the rungs below, a timer begins to increment for anymiscompare between the actual output bit and its associatedData Echo bit. The timer must be preset to accommodate thedelay between setting the output bit in controller memory andreceipt of the Data Echo from the module. If a miscompareexists for longer than that time, a fault is reported.Figure 6.6Application LogicActuatorOutput BitData EchoTimerOutput BitData EchoTimer doneFaultFaultAlarm to OperatorPublication 1756-RM001B-EN-P - October 2003