Siemens SIMATIC S7-1500 System Manual page 313

Configuration
9.9 Display of the IO device assignments in STEP 7
Reference
Calculation of the PROFIsafe monitoring time
For the calculation of the PROFIsafe monitoring time you will find the times RDHT [ms] and
MTOT [ms] in the right area of the "I/O communication" view.
Figure 9-16
Time information RDHT: Redundancy Data Hold Time. RDHT indicates the time duration, how
long the outputs of an IO device are not updated during AR switching before the IO device
fails.
Time information MTOT: Maximum Take over Time. MTOT indicates the time duration how
long the inputs of an IO device are not updated during AR switching before the IO device
fails.
Valid values for RDHT and MTOT are only displayed after you have compiled the STEP 7
project. If you change the hardware configuration afterwards, you have to recompile the
project. After the compile STEP 7 shows valid values again.
For more information, refer to the following entry on the Internet
(https://support.industry.siemens.com/cs/ww/en/view/93839056) and in the SIMATIC Safety -
Configuring and Programming
(https://support.industry.siemens.com/cs/ww/en/view/54110126) programming and
operating manual.
312
Display of time information RDHT and MTOT
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF