Exception Conditions - Siemens SIMATIC S7 System Manual

11.5

Exception conditions

Warning conditions
Tuning execution can generate three warning conditions. Tuning execution reports these
warnings in three bits of the ASTAT field of the loop table, and, once set, these bits remain
set until the next auto-tune sequence is initiated:
● Warning 0: Generated if the deviation value is not at least 4X greater than the hysteresis
value. This check is performed when the hysteresis value is actually known, which
depends upon the auto-hysteresis setting.
● Warning 1: Generated if there is more than an 8X difference between the two peak error
values gathered during the first 2.5 cycles of the auto-tune procedure
● Warning 2: Generated if the measured average peak error is not at least 4X greater than
the hysteresis value
Error conditions
In addition to the warning conditions, several error conditions are possible. The following
table lists the error conditions, along with a description of the cause of each error.
Table 11- 3 Error conditions during tuning execution
Result code (in ARES)
01 aborted by user
02 aborted due to a zero-crossing watchdog
timeout
03 aborted due to the process out-of-range
04 aborted due to hysteresis value exceeding
maximum
05 aborted due to illegal configuration value
06 aborted due to a numeric error
07 PID instruction was executed with no power
flow (manual mode)
08 auto-tuning allowed only for P, PI, PD, or PID
loops
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Condition
EN bit cleared while tuning is in progress
Half-cycle elapsed time exceeds zero-crossing watchdog interval
PV goes out-of-range:
during the auto-hysteresis sequence, or
•
twice before the fourth zero-crossing, or
•
after the fourth zero crossing
•
User-specified hysteresis value, or
automatically determined hysteresis value > maximum
The following range checking errors:
Initial loop output value is < 0.0 or > 1.0
•
User-specified deviation value is <= hysteresis value, or is >
•
maximum
Initial output step is <= 0.0 or is > maximum
•
Zero-crossing watchdog interval time is < minimum
•
Sample time value in loop table is negative
•
Illegal floating point number or divide by zero encountered
PID instruction executed with no power flow while auto-tuning is in
progress or is requested
Loop type is not P, PI, PD, or PID
PID loops and tuning
11.5 Exception conditions
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