Siemens SIMATIC Manual page 506

Other signal modules
7.4 Position decoder module SM 338; POS-INPUT; (6ES7338-4BC01-0AB0)
Parameters
Monoflop time 1),2),3)
Scaling
•
Places
•
Steps per revolution 4
Enabling the Freeze function
1 Refer to the technical specifications of the absolute value encoder
2 The monoflop time represents the interval between two SSI frames. The configured mon-
oflop time must be greater than the monoflop time of the absolute value encoder (see the
technical data of the manufacturer). The time 2 x (1 / transmission rate) is added to the
value set in HW Config. A transmission rate of 125 kHz and configured monoflop time of
16 µs sets an effective monoflop time of 32 µs.
3 Restriction of the monoflop time of the absolute value encoder:
(1 / transmission rate) < monoflop time of the absolute value encoder < 64 µs + 2 x (1 /
transmission rate)
4 to powers of two
Note
Please note that in asynchronous mode, the transmission rate and monoflop time affect the
accuracy and update quality of the encoder values. In isochronous mode, the transmission
rate and monoflop time have an influence on the accuracy of the freeze function.
506
Range of values
16 µs; 32 µs; 48 µs; 64 µs
0 to 12
2 to 8192
off; 0; 1
Note
The monoflop time represents the minimum inter-
val between two SSI frames.
The configured monoflop time must be greater
than the monoflop time of the absolute value
encoder.
Scaling right-aligns the encoder value in the ad-
dress space; irrelevant places are discarded.
Definition of the digital input that initiates freezing
of the encoder value at the positive edge.
Manual, 06/2017, A5E00105505-AJ
S7-300 Module data