Chapter 15 PID Function (Built-in function) 
 
15 - 37 
 
 
 
15.4.4 Auto-tuning flag 
 
The parameters set in the XGB series auto-tuning function are saved to the flash memory of basic unit. 
Such parameters are moved to K area for auto-tuning function as soon as PLC enters to RUN mode 
from STOP. Auto-tuning operation using auto-tuning command is achieved by data in K area. At the 
moment, if PLC is changed to RUN again after being changed to STOP, it takes the parameters in 
flash memory to K area, so the data changed in K area is lost. Therefore, to continuously apply the 
parameters adjusted in K area, it is necessary to write the parameters set in K area into flash memory 
by using WRT command. (In case of IEC type, APM_WRT function block) 
   
(1) Auto-tuning flag configuration 
 The K area flags of XGB series auto-tuning function are summarized in Table 15.12.   
Auto-tuning direction(0:forward,   
1:reverse) 
PWM output enable(0:disable,   
1:enable) 
Auto-tuning 
error(0:normal,1:error) 
AT operation cycle 
(T_s)[0.1msec] 
AT auto-tuning status indication 
AT result proportional coefficient 
AT result differential time 
[Table 15.12 K area flags for auto-tuning] 
K1856 ~ K1859 areas (In case of IEC type, %KW1856~%KW1859) are the common bit areas for 
auto-tuning and each bit represents auto-tuning loop status respectively. K1860~K1879 areas save 
the setting and status of loop 0 as the K area for auto-tuning loop 0. In the area, the parameters 
such as PV, operation cycle and etc set in the built-in parameter window are saved and the XGB 
built-in auto-tuning function executes auto-tuning by the device values and saves the results into the 
K areas.