Siemens SIMATIC S5 Manual page 126

Byte 16 Error bytes 0 to 12
to 28
Explanation of the line break identifier A, B (for Pt 100 and thermocouples):
If linearization of the characteristic curve was disabled (bit 3, control byte 2 = 1), the sensors are
not checked for defects (external sensor modules are then connected).
It is only possible to check thermocouples indirectly for short circuits. With the Pt 100, direct and
indirect short circuit monitoring is possible (indirect short circuit monitoring by means of an entry
in messages 30 to 42 and signalling via message 46).
IP244
C79000–B8576–C860–02
Data Exchange with the Central Controller
4–59