Siemens SIMATIC S7-1200 Function Manual page 500

Instructions
9.4 PID basic functions
Manual value processing (LMNS_ON, LMNUP, LMNDN)
With LMNS_ON, you can change between manual and automatic mode. In manual mode,
the actuator is halted and the integral action (INT) is set to 0 internally. Using LMNUP and
LMNDN, the actuator can be adjusted to OPEN and CLOSED. Switching over to automatic
mode therefore involves a bump. As a result of the GAIN, the existing control deviation leads
to a step change in the internal manipulated variable. The integral component of the
actuator, however, results in a ramp-shaped excitation of the process.
See also
Block diagram TCONT_S (Page 501)
500
Function Manual, 03/2017, A5E35300227-AC
PID control