Siemens SIMATIC S5 Manual page 124

Bit 6 Following a power failure, the IP sets the "parameter request" bit when the power
returns. The PLC must then transfer messages 0 to 15 and 30 to 42 and on
completion of the transfer set bit "parameter transfer complete" (in main control
byte 4). This resets the request from the IP 244. If this does not happen, the IP is
placed in a queue. The digital outputs are OFF, the IP does not read any actual
values and the controllers are not processed.
Bit 7 This bit changes its state at least once every one second.
This allows the user program in the PLC to recognize a "program crash" on the IP.
Byte 1 Free
Byte 2/3 Controller group error/channel group error
The bit assigned to the controller/channel is set if an error bit is set in the
corresponding error bytes in message 16 and 46.
Assignment of the bits to the controllers:
*) With the variant -3AB31, the error message is also set when the 24 V supply is
missing. This error can also occur if the external wiring is missing or if the fuse on
the module fails.
Byte 4/5 Self-tuning status
If the module performs a self-tuning run for one or more controllers, the bit
assigned to the controller is set. Once the self-tuning function is complete, the
corresponding bit is reset (see also Section 1.2). If parameters were successfully
calculated, this is indicated in message 0 to 12, byte 23.
IP244
C79000–B8576–C860–02
Data Exchange with the Central Controller
4–57