Siemens Simatic S7 Series System Manual page 470

PID loops and tuning
11.1 PID loop definition table
Table 11- 2 Expanded description of control and status fields
Field
AT Control (ACNTL)
Input - Byte
AT Status (ASTAT)
Output - Byte
AT Result (ARES)
Input/Output - Byte
470
Description
EN Set to 1 to start auto-tune; set to 0 to abort auto-tune
W0 Warning: The deviation setting is not four times greater than the hysteresis set-
ting.
W1 Warning: Inconsistent process deviations may result in incorrect adjustment of the
output step value.
W2 Warning: Actual average deviation is not four times greater than the hysteresis
setting.
AH Auto-hysteresis calculation in progress:
0 - not in progress
1 - in progress
IP Auto-tune in progress:
0 - not in progress
1 - in progress
Each time an auto-tune sequence is started the CPU clears the warning bits and sets the in
progress bit. Upon completion of auto-tune, the CPU clears the in progress bit.
①
Result code
D Done bit:
0 - auto-tune not complete
1 - auto-tune complete
Must be set to 0 before auto-tune can start
Result 00 - completed normally (suggested tuning values available)
Code
01 - aborted by the user
02 - aborted, watchdog timed out waiting for a zero crossing
03 - aborted, process (PV) out-of-range
04 - aborted, maximum hysteresis value exceeded
05 - aborted, illegal configuration value detected
06 - aborted, numeric error detected
07 - aborted, PID instruction executed without having power flow (loop in manual
mode)
08 - aborted, auto-tuning allowed only for P, PI, PD, or PID loops
09 to 7F - reserved
System Manual, 09/2015, A5E03822230-AC
S7-200 SMART