Siemens SIMATIC S5 Manual page 264

Appendix
A.2.3
Controller is enabled by:
– command "ST" for the respective controller, or
– commands "CR" or "PA"
and by entering a setpoint not equal 0.
(The steps "CR" or "PA" and setpoint
The self-tuning function is now active.
– Status bits in DB-B, message 16, DW 34. As long as the self-tuning function is
active, the bit for each controller is set and is reset by the IP on completion of the
function.
– Control using the entered setpoint following the tuning.
If heating and cooling parameters have been determined during the self-tuning
phase, this is indicated in DB-A, messages 0 to 12, DR n + 11.
A.2.4 Caution!
If a controller is already running with self-tuning function and another controller is
being changed parameters with "AE", then the self-tuning function for the first
controller also starts anew (this is necessary, as with AE also the structure of the
controllers and the output allocation can be changed).
After "AE" has been used, all conditions for the self-tuning controller must still be met.
A.2.5 Caution!
If a power failure occurs during the self-tuning function, the calculated parameters are
useless. Then a new minimum setpoint jump (see section A.1) must be provided. The
height of the minimum jump for each three-step controller is output in DB-A,
DL n + 15 (messages 0 to 12). This is possible either by cooling down the process
and restarting it (e.g. switch over to manual operation and colling with three-step
controllers) or by means of a minimum setpoint jump from the current actual value on.
A.2.6 Caution!
If a power failure occurs following the self-tuning phase, the controller will continue to
operate with the calculated parameters when the power returns, if you:
– read all the calculated parameters (the FB does this automatically if DR6 DB-A,
bit 0 = 1),
– clear all DL n +11 (message 0 to 12) except bit 1 in DB-A:
– transfer all calculated parameters back to the IP.
Further advantages:
– the calculated parameters are not lost even if the battery back-up of the IP fails,
– the self-tuning function is not restarted by KS during the start-up,
– the self-tuning is not repeated if the battery back-up of the IP fails.
5–60
0 can be combined.)
C79000–B8576–C861–02
IP244