Siemens SIMATIC S5 Manual page 94

Byte 6 2nd positive tolerance
If the actual temperature is above the setpoint plus the second positive tolerance,
an error identifier is set (bit 2 in the appropriate error byte) and the controller is
switched off, if this has been selected in main control byte 4, bit 7. If the value 0
is entered, the tolerance is not effective.
Byte 7 2nd negative tolerance
If the actual temperature is below the setpoint minus the second negative
tolerance, an error identifier is set (bit 3 in the appropriate error byte) and the
controller is switched off, if this has been selected in main control byte 4, bit 7.
If the value 0 is entered, the tolerance is not effective.
Byte 8/9 Control bytes 1 and 2
The functions to be carried out are fixed in control byte 1 and 2 (bytes 8 and 9) in
the message for the controller channel whose number is written in byte 31.
Byte 8 Control byte 1
IP244
C79000–B8576–C860–02
Data Exchange with the Central Controller
4–27