Siemens SIMATIC S5-100U System Manual page 451

S5-100U
Performance during Overflow
If the counter leaves the counting range of -32,768 to + 32,767, then the following occurs:
• Bit 3 (overflow) in the diagnostic byte is set to "1".
• The outputs of the counter module are disabled.
The enable input (terminal 4 of the terminal block) must be set to "0", in order to switch off active
outputs.
After an overflow, a new reference point approach operation has to be executed for synchronization
of the actual value detection. After reaching the synchronization, bit 3 in the diagnostic byte is again
set to "0", and the outputs along with the active enable input can be turned on.
Note
During an overflow, active outputs are not switched off, and the SYNC bit (bit 0 in the
diagnostic byte) is not reset.
EWA 4NEB 812 6120-02b
Function Modules
15-37