7 SSI Input Units
7 - 18
NX-series Position Interface Units User’s Manual (W524)
Use synchronous I/O refreshing to synchronize the timing of SSI communications data (i.e., the timing
of obtaining the data) for one or more SSI Input Units with the processing of the Controller.
The SSI Input Unit will refresh data through SSI communications synchronously with the Controller pro-
cessing cycle.
Data is exchanged with the Controller based on the I/O refreshing timing of the Controller.
The data that is exchanged is based on the SSI data that was obtained in the last I/O refresh.
*1. For an NX-series CPU Unit, the task period of the primary periodic task or priority-5 periodic task is applica-
ble. For an NJ-series CPU Unit, only the task period of the primary periodic task is applicable.
Note Refer to Operation of Synchronous I/O Refreshing on page 5-7 for details.
For this method, the SSI Input Unit sends a clock signal to the encoder based on the synchronization
cycle and receives data from the encoder.
After the data is received, the updated data is written to memory for I/O refreshing.
The period for receiving and refreshing data through SSI communications depends on the SSI baud
rate and data length, just as it does for Free-Run refreshing.
The calculation method for the data refresh cycle is the same as for Free-Run refreshing. The timing of
refreshing the data that is exchanged with the Controller depends on the data refresh cycle of the SSI
communications.
You can use data traces on the Sysmac Studio to check the data update timing. Use a data trace to
check the timing when the value of the Data Refresh Status bit in the SSI Status changes. Or, assign
the Encoder Present Position Refresh Count to an output and check the timing when the value changes
in the data trace.
Refer to 7-6-2 Free-Run Refreshing on page 7-15 for details.
If the Wait Time for Receive Enabled parameter is set, SSI communications processing is started again
at the next synchronization cycle after the value set for the Wait Time for Receive Enabled parameter
elapses from when the data is refreshed.
Precautions for Correct Use
If you use synchronous I/O refreshing, set the task period to a value within the specified refresh
cycle range of the Position Interface Unit.
7-6-3 Synchronous I/O Refreshing
I/O refreshing
Data received and refreshed Data received and refreshed
I/O refreshing
Controller
SSI Input Unit
Controller cycle
time
*1
Position data
Clock output
Data input
Data refresh cycle
Synchronization cycle Synchronization cycle
Wait Time for
Receive Enabled
Data
processing
Data
processing
To Next Page
Loading...
Need help?
General
