Checking The Validity Of The Process Data - Omron NX701-17 Series User Manual

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Checking the Validity of the Process Data

When reading and writing the device variables and axes variables that input and output process data
with slaves, the validity of the process data must be checked.
When EtherCAT communications are not established, such as immediately after the power supply to
the CPU Unit is turned ON, the process data is invalid. Thus values become invalid for the device vari-
ables and axes variables that input and output the process data. If EtherCAT communications were
established previously, the device variables and axes variables retain the values updated while Ether-
CAT commutations were established then.
Once the EtherCAT communications are established, the process data becomes valid, therefore values
of the device variables and axes variables which input and output the process data become also valid.
Be sure to read and write the device variables and axes variables that input and output the process
data, after confirming that the process data is valid.
Use the following system-defined variables to check the validity of the process data.
• Checking the validity of the process data for each slave.
_EC_PDSlavTbl (Process Data Communicating Slave Table)
• Checking the validity of the process data for the entire slaves.
_EC_PDActive (Process Data Communications Status)
Precautions for Correct Use Precautions for Correct Use
If noise occurs or an EtherCAT slave is disconnected from the network, any current communica-
tions frames may be lost. If frames are lost, slave I/O data is not communicated, and unintended
operation may occur. The slave outputs depend on the slave specifications. For details, refer to
relevant manuals for each slave. If a noise countermeasures or slave replacement is required,
perform the following processing.
• Program the _EC_InDataInvalid (Input Data Invalid), _ECIndata1Invalid (Input Data1 Invalid),
or _EC_InData2Invalid (Input Data2 Invalid) system-defined variable as an interlock condition
in the user program.
• Set the PDO communications timeout detection count setting in the EtherCAT master to 2 or
higher. Refer to 5-4-1 Setting EtherCAT Master for the setting procedure.
A sample programming to check the validity of the process data is shown in the next section.
NJ/NX-series CPU Unit Built-in EtherCAT Port User's Manual (W505)
6 Process Data Communications and SDO Communications
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