8.8 Hard Wire Base Block (HWBB) Function8-41 Operation88.8.10 External Device Monitor (EDM)The external device monitor (EDM) functions to monitor failures in the HWBB function. The relation of theEDM, /HWBB1, and /HWBB2 signals is shown below. Failure Detection Signal for EDM SignalDetection of failures in the EDM circuit can be checked using the following four status of the EDM signalin the table. Connection ExampleThe connection example of EDM signal is shown below.SignalName Logic/HWBB1 ON ON OFF OFF/HWBB2 ON OFF ON OFFEDM OFF OFF OFF ONFor HWBB function signal connections, the input signal is the 0 V common and the outputsignal is the source output. This is opposite to other signals described in this manual. Toavoid confusion, the ON and OFF status of signals for HWBB function are defined as follows:ON: The state in which the relay contacts are closed or the transistor is ON and currentflows into the signal line.OFF: The state in which the relay contacts are open or the transistor is OFF and no cur-rent flows into the signal line.Host controllerEDM!+EDM!-0 V24-V power supplySERVOPACK
