Siemens Simatic series Manual page 32

Behavior when a counting limit is exceeded - Continue counting
The following section describes the effects of the parameter "Behavior when a counting limit
is exceeded = Continue counting". To control the counter, the bits of the control byte of the
control interface are used, see section Address space Counting mode (Page 25), subsection
Control interface.
Counting begins at the current counted value (the SW-GATE is set in the control byte). Bit
sequence in the control byte of the control interface 0000 1000.
After the high counting limit is exceeded, the counted value jumps to the low counting limit =
0 and counting is continued.
If the SW_GATE bit is reset in the control byte of the control interface before reaching the
high counting limit, counting is stopped.
The following figure shows an example of the principle of continuing counting when a
counting limit is exceeded.
Figure 4-10 Principle: Continue counting
DI 16x24VDC HF Digital Input Module (6ES7521-1BH00-0AB0)
Manual, 08/2018, A5E03485952-AG
Parameters/address space
4.2 Address space
31