Siemens SIMATIC ET 200S Manual page 58

Addressing
User Data Transfer in STOP Mode
The user data in the intermediate memory is processed differently depending on
whether the DP master or the DP slave (IM 151-7 CPU) goes into STOP mode.
S If the IM 151-7 CPU goes into STOP mode: The data in the intermediate
memory (outputs only from the slave's viewpoint) of the IM 151-7 CPU are
overwritten with "0"; i.e. the DP master or a recipient in direct communication
reads "0".
S If the DP master goes into STOP mode: The current data in the intermediate
memory of the IM 151-7 CPU (inputs in the slave, outputs in the master) are
retained and can be read out in the user program of the IM 151-7 CPU.
S5 DP master
If you use the IM 308–C as a DP master and the IM 151–7 CPU as an I slave, the
following applies to the exchange of consistent data:
You must program FB 192 in the IM 308–C to enable the transfer of consistent
data between the DP master and the I slave. The effect of FB 192 is that the data
of the IM 151–7 CPU is only output or read out continuously in a single block.
3-10
ET 200S IM 151-7 CPU Interface Module
A5E00058783-04