Siemens SIMATIC S7 - Normal Operation

5-7
SM 338 Equipment Manual
(4) J31069-D401-U1-A0-7618
5.3 Normal Operation
After the parameters have been assigned correctly, the SM 338 functions in
normal operation. This is signaled by the LEDs as shown below.
S DC (green) on
S SF (red) off
Depending on the parameter assignment, the measured values of a sensor are
updated synchronously (i. e ., at the end of the cycle time) or asynchronously
(i.e., at the end of the measuring cycle time).
The sensor values can then be read in by the user program and evaluated.
Note
Each counting value consists of 2 bytes or 1 word (i .e., data consistency re-
quires that the counting values be fetched via “l oad I/O input word”).
O
p
e
r
a
tion