Siemens SIMATIC S7-400H System Manual page 455

Restrictions of the fault-tolerant CPU compared to a standard CPU
Function
Hot restart
Multicomputing
Startup without configuration
loaded
Background OB
Multi-DP master mode
Direct communication between
DP slaves
Constant bus cycle time for DP
slaves
Synchronization of DP slaves
Disabling and enabling DP
slaves
Runtime response
DP cycle time
Delays and inhibits
Use of symbol-oriented
messages (SCAN)
Global data communication
S7 basic communication
S5 connection
CPU as DP slave
CPU as I-Device
S7-400H
System Manual, 03/2012, A5E00267695-11
Differences between fault-tolerant systems and standard systems
Restriction of the fault-tolerant CPU
A hot restart is not possible. OB 101 is not possible
Multicomputing is not possible. OB 60 and SFC 35 are not
supported
Startup without loaded configuration is not possible.
OB 90 is not supported.
The fault-tolerant CPUs do not support multi-DP master mode in
REDUNDANT mode.
Cannot be configured in STEP 7
No constant bus cycle time for DP slaves in the fault-tolerant
system
Synchronization of DP slave groups is not supported. SFC 11
"DPSYC_FR" is not supported.
Disabling and enabling DP slaves is not possible. SFC 12
"D_ACT_DP" is not supported.
The command execution time for a CPU 41x–5H is slightly higher
compared to the corresponding standard CPU (see
Instruction List
and
into account for all time-critical applications. You may need to
increase the scan cycle monitoring time.
A CPU 41x-5H has a slightly longer DP cycle time compared to
the corresponding standard CPU.
During update:
The asynchronous SFCs for data records are acknowledged

negatively
Messages are delayed

All priority classes up to 15 are initially delayed

Communication jobs are rejected or delayed

Finally, all priority classes are disabled

For more detailed information, refer to chapter 7.
The use of symbol-oriented messages is not possible.
GD communication is not possible (neither cyclically, nor by
calling system functions SFC 60 "GD_SND" and SFC 61
"GD_RCV")
Communication functions (SFCs) for basic communication are not
supported.
The connection of S5 modules by means of an adapter casing is
not possible. The connection of S5 modules via IM 463-2 is only
supported in stand-alone mode.
Not possible
Not possible
S7-400H Instruction List
). This must be taken
S7–400
455