Omron NX-EC0112, User Manual

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7 SSI Input Units
7 - 28 NX-series Position Interface Units User’s Manual (W524)
When you assign the SSI Input Unit to an encoder axis in the MC Function Module, the MC Function
Module monitors the bit that corresponds to the SSI Input Unit in the Process Data Communications
Status.
You can assign the Process Data Communications Status as an EtherCAT Coupler Unit device vari-
able.
This allows the MC Function Module to perform error processing if valid input data is not passed to the
Controller during operation of the SSI Input Unit. The MC Function Module also uses this to set the
present position of the encoder axis when the initial encoder value is read after the SSI Input Unit starts.
However, if reading the initial value is not possible, the SSI Input Unit cannot begin operation normally
and the SSI Input Unit sets the bit in the SSI Communications Error Status in the SSI Status.
The bit in the Process Data Communications Status is also set at this time.
Because the encoder present position is still set to the default value of 0 at this time, the MC Function
Module cannot set the initial position of the encoder axis to the correct value.
Therefore, when you assign an SSI Input Unit to an MC Function Module encoder axis, always check to
confirm that the bit in the SSI Communications Error Status in the SSI Status was reset when the bit in
the Process Data Communications Status for the SSI Input Unit is set before you use the encoder axis.
If the bit in the SSI Communications Error Status is still set when bit in the Process Data Communica-
tions Status for the SSI Input Unit is set, the initial position of the encoder axis will not be set correctly. If
this occurs, correct the problem that caused the SSI communications error and restart the NX Unit so
that the SSI Input Unit beings operation correctly.
You can access the SSI Status and SSI Communications Error Code as device variables of the SSI
Input Unit, even if the Unit is assigned and used as an encoder axis.
Precautions When Assigning an SSI Input Unit to an MC Function
Module Axis
NJ/NX-series CPU Unit
Process Data Communications Status
Bit corresponding to the SSI Input Unit
EtherCAT
Coupler Unit
SSI Input
Unit
SSI input
data
EtherCAT
Motion Control Function Module
Encoder Axis Present Position
The present position is determined
when the bit that corresponds to the
SSI Input Unit (01) is set.
Bit in Process Data
Communications Status that
corresponds to SSI Input Unit
SSI Communications Error
Status
The cause of the error is removed.
Incorrect present position
Encoder axis present position
(MC Function Module axis
variable)
Power
turned ON
or Unit
restarted. Process data
communications started
(SSI error)
→
Encoder axis
present position determined.
Unit
restarted. Process data
communications started
→
Encoder axis present
position determined.