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These 10 free C-310 questions are organized by exam domain, so you can see how each part of the Ethernet Communications 2 blueprint is tested. Reveal the answer and explanation under each question.
A remote valve manifold stops actuating its valves. Its Ethernet adapter remains connected to the PLC, input switches still update, and the manifold's output-command indicators follow the PLC commands. The adapter electronics and valve coils have separate 24 V supplies. Where should the first diagnostic checks concentrate?
Correct answer: C - The valve-coil supply and its common field-power circuit
A Logix calculation intermittently combines one remote I/O record's count with the next record's measured length. The adapter delivers each record as a complete, consistent unit. Only asynchronous I/O updates can change the input structure during execution. Which change prevents the calculation from mixing two received records?
Correct answer: B - Capture the structure once with CPS, then calculate from the captured buffer.
A PLC sends a release-one-part request with transaction ID 427, then times out without a reply. The dispenser records active and completed transaction IDs but does not suppress duplicate requests. The chute is out of view, and no other controller issues releases. Before requesting another part, the PLC should:
Correct answer: D - Read the active and last completed transaction IDs.
Adding an optional maintenance read produces CIP general status 0x14, 'Attribute not supported.' Two other attributes in the same class and instance can be read successfully, and cyclic I/O remains healthy. The appropriate response is to:
Correct answer: D - Correct the requested attribute for this device revision.
Temperature and SampleID arrive from a heater controller through cyclic EtherNet/IP I/O. SampleID advances after every completed acquisition, even when temperature is unchanged. Valid I/O packets keep arriving every 10 ms, but SampleID has not advanced for 600 ms. The receiving application allows a measurement age of no more than 300 ms. How should the receiver classify this condition?
Correct answer: C - Stale application data over an active I/O connection.
During commissioning, a PLC starts and stops a conveyor drive reliably over EtherNet/IP. The drive's diagnostics show that the received network speed-reference value follows the PLC command, but output frequency responds only to the cabinet potentiometer. The drive is now stopped. Which correction fits these observations?
Correct answer: A - Select Ethernet as the drive's active speed-reference source.
At a U.S. plant, an electrician is preparing to disconnect the motor conductors on a VFD-controlled conveyor. An Ethernet stop has been issued, Safe Torque Off is active, and the shaft is stationary; the drive remains connected to its supply. Before the conductors are touched, which condition must be established?
Correct answer: C - Locked-out energy sources, controlled stored energy, and verified absence of voltage
Two cell switches are joined by an operational 802.1Q trunk. A PLC on the first switch and an HMI on the second use access VLAN 20 and unique addresses in the same IP subnet. Each communicates with a test laptop on its own switch. VLAN 20 exists on both switches, but both trunk ports permit only VLANs 10 and 99. What restores the intended path?
Correct answer: D - Add VLAN 20 to the permitted list on both trunk ports.
Only a maintenance laptop's IPv4 settings may be changed during a connection test. Its switch port is already in the PLC's VLAN. The PLC uses 192.168.10.70/26, no router serves this VLAN, and all candidate laptop addresses are unused. Select the laptop configuration that permits direct communication with the PLC.
Correct answer: A - 192.168.10.100 with mask 255.255.255.192
Moving a packaging machine's wireless antenna changes the measured signal from -66 to -58 dBm and the noise floor from -94 to -76 dBm. This installation requires received power of at least -70 dBm and a signal-to-noise ratio of at least 22 dB. How should the proposed antenna position be assessed?
Correct answer: B - Reject it: its current signal-to-noise ratio is 18 dB.
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