Siemens SIMATIC S7 - 3.3 Interface to the CPU

4-7
SM 338 Equipment Manual
(4) J31069-D401-U1-A0-7618
The SM 338 can generate an end-of-cycle alarm (i.e., process alarm 0) at the
end of the cycle time set. This requires that generation be enabled in byte 1
of data record 0.
Cycle time
00000 16.0msec
00001 0.5msec
00010 1.0msec
..
..
..
11111 15.5msec
70
Byte 14
000
In synchronous mode, the sensor operates with the cycle time for alarm gen-
eration in byte 14 of data record 1, and not with its preset measuring cycle
time. In synchronous mode, new measured values are supplied a t the same
time as the end-of-cycle.
Synchronous mode
Sensor 1
Sensor 2
Sensor 3
Sensor 4
0: Asynchronous
1: Synchronous
70
Byte 15
0000
Note
When one or more sensors are operated in synchronous mode , it is abso-
lutely imperative that the cycle time be adjusted to the slowest sensor. The
module does not perform a plausibility check of this.
Cycle time
Sensor-related
synchronous
mode
D
a
t
a
Communic
a
tion with the PLC