7 SSI Input Units
7 - 56
NX-series Position Interface Units User’s Manual (W524)
*1. The difference is greater than the limit, so the obtained data is discarded and the current data is not
refreshed. The difference is then set to 0.
*2. If the present position of the encoder is not refreshed because of the discarded data, the present position
refresh bit is also not toggled. The Encoder Present Position Refresh Count and Time Stamp parameters are
also not refreshed.
When you obtain SSI data from an SSI Input Unit and the position data has changed from the previ-
ously obtained position data, you can obtain the DC time when that change occurred along with the
data.
Position data is obtained when NX bus I/O is refreshed.
The obtained position data and DC time are input to the Controller.
The obtained DC time is called a time stamp.
Timing Charts
7-9-9 Time Stamping
0
Obtained data
Differential data
Position variation limit
Position variation limit
Encoder present
position
(refreshed data)
Present value
refresh bit
Time
(SSI communications cycle)
Time
(SSI communications cycle)
Time
(SSI communications cycle)
(*1)
(*1)
(*2) (*2)
Position data
I/O refreshing
on NX bus
DC time
obtained.
DC time
obtained.
DC time
obtained.
DC time not
obtained.