Siemens SIMATIC S7-400H - Page 455

Differences between fault-tolerant systems and standard systems
S7-400H
System Manual, 03/2012, A5E00267695-11
455
Restrictions of the fault-tolerant CPU compared to a standard CPU
Function Restriction of the fault-tolerant CPU
Hot restart A hot restart is not possible. OB 101 is not possible
Multicomputing Multicomputing is not possible. OB 60 and SFC 35 are not
supported
Startup without configuration
loaded
Startup without loaded configuration is not possible.
Background OB OB 90 is not supported.
Multi-DP master mode The fault-tolerant CPUs do not support multi-DP master mode in
REDUNDANT mode.
Direct communication between
DP slaves
Cannot be configured in STEP 7
Constant bus cycle time for DP
slaves
No constant bus cycle time for DP slaves in the fault-tolerant
system
Synchronization of DP slaves Synchronization of DP slave groups is not supported. SFC 11
"DPSYC_FR" is not supported.
Disabling and enabling DP
slaves
Disabling and enabling DP slaves is not possible. SFC 12
"D_ACT_DP" is not supported.
Runtime response The command execution time for a CPU 41x–5H is slightly higher
compared to the corresponding standard CPU (see
S7–400
Instruction List and S7-400H Instruction List ). This must be taken
into account for all time-critical applications. You may need to
increase the scan cycle monitoring time.
DP cycle time A CPU 41x-5H has a slightly longer DP cycle time compared to
the corresponding standard CPU.
Delays and inhibits 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.
Use of symbol-oriented
messages (SCAN)
The use of symbol-oriented messages is not possible.
Global data communication GD communication is not possible (neither cyclically, nor by
calling system functions SFC 60 "GD_SND" and SFC 61
"GD_RCV")
S7 basic communication Communication functions (SFCs) for basic communication are not
supported.
S5 connection 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.
CPU as DP slave Not possible
CPU as I-Device Not possible