Siemens SIMATIC S5 Manual page 123

Data Exchange with the Central Controller
Byte 0 Status byte 1
Byte 0 Status byte 1
Bit 0 The group error bit is always set when a bit is set in one of the error bytes 0 to 14
or 0a to 12a in message 46, or if the Pt 100 has a fault.
Bit 1 Free
Bit 2 Acknowledgement bit for measured value acquisition at channel 13. The start of
this function clears the bit, the end of the function sets the bit.
Bit 3 Acknowledgement bit for single measurement at channel 14. The start of the
function clears this bit, the end of the function sets this bit.
Bit 4 Free (always 0)
Bit 5 When the PLC accesses the IP, the IP processor is blocked. If the access takes
too long, a sampling time overflow may occur. An "access rate" of one message
per 100 ms is acceptable.
4–56
IP244
C79000–B8576–C860–02