Topic: DMD0273
Device List
The Devices Dialog
The Devices dialog lists all of the Device that have been created in the currently open project. Double-clicking on any device in the Device dialog will open a Device Status dialog which will display run-time status of that device.
Name is automatically given to the Device by the system, or manually assigned by the programmer. This name can be changed on the Device Configuration page of the System Configuration utility.
Description is a short description of the Device. If there is an error obtaining information about the Device, the description will contain one of the following two terms:
UNRESOLVED means the device name is valid but the communication requests to get the status information from the device failed.
OFFLINE means the project is open while NOT connected to the PLC.
Device Status
Because Devices are shared resources in the PLC, and the activities that Devices perform generally take multiple PLC scans, an instruction will "lock" a Device when it begins using it and will "unlock" the Device when the instruction is complete. This Locking / Unlocking protocol has the potential of locking a Device indefinitely, which will prevent that Device from being accessible by any other instruction. For example, if an instruction in a Task or Program locks a Device, and that Task or Program is Suspended before the instruction finishes, the Device will remain locked until that instruction has a chance to complete. The Device Status dialog will display the runtime state of that Device.
Device Name is the name given to the Device by the system, or assigned by the programmer. The number in parenthesis is the system-assigned DeviceID.
Idle Time displays the amount of time (in microseconds) that has elapsed since the Device was last accessed. This value will typically be in the range of 0 - 400 for a Device that is working normally. A larger non-Zero value indicates that the Device is locked by an instruction that is not accessing the Device. Idle Time values will be displayed with colored backgrounds as follows:
0 - 400 milliseconds - (Green) indicates the device is Ok
401 - 1600 milliseconds - (Yellow) indicates the Device is being locked for relatively long periods of time
1601 + milliseconds - (Red) indicates the Device is locked and likely causing problems, this is typically caused by programming errors such as improperly formed looping instructions, or by suspending a code-block that is using a Device
Locked Instruction will show which instruction currently has the Device locked. It will display the Instruction Name, the Program Block, and the address of the instruction within that block. For example "MRX $Main@27" is the Modbus Network Read (MRX) instruction in the Program $Main, at address 27. Entries in the Locked instruction column are hyper-links; clicking on any of these entries will open that code block in a Ladder View tab and place the edit cursor on that instruction.
LastError is the error code that was reported by the Device
State specifies the current state of the Device, either Open (currently in use by an instruction) or Closed (not currently in use by any instruction).
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