Recommendations For Setting The Cpu Parameters - Siemens SIMATIC S7-400H System Manual

Configuring with STEP 7
15.1 Configuring with STEP 7
15.1.4

Recommendations for setting the CPU parameters

CPU parameters that determine cyclic behavior
You specify the CPU parameters that determine the cyclic behavior of the system on the
"Cycle/Clock memory" tab.
Recommended settings:
● As long a scan cycle monitoring time as possible (e.g. 6000 ms)
● OB 85 call when there is an I/O area access error: only with incoming and outgoing errors
Number of messages in the diagnostic buffer
You specify the number of messages in the diagnostic buffer on the "Diagnostics/Clock" tab.
We recommend that you set a large number (3200, for example).
Monitoring time for transferring parameters to modules
You specify this monitoring time on the "Startup" tab. It depends on the configuration of the
fault-tolerant station. If the monitoring time is too short, the CPU enters the W#16#6547
event in the diagnostic buffer.
For some slaves (e.g. IM 157) these parameters are packed in system data blocks. The
transmission time of the parameters depends on the following factors:
● Baud rate of the bus system (high baud rate => short transmission time)
● Size of the parameters and the system data blocks (long parameter => long transmission
● Load on the bus system (many slaves => long transmission time);
Recommended setting: 600 corresponds to 60 s.
Note
The specific fault-tolerant CPU parameters, and thus also the monitoring times, are
calculated automatically. The work memory allocation of all data blocks is based on a CPU-
specific default value. If your fault-tolerant system does not link up, check the data memory
allocation (HW Config > CPU Properties > H Parameters > Work memory used for all data
blocks).
NOTICE
A CP 443-5 Extended (order number 6GK7443–5DX03) may only be used for transfer rates
of up to 1.5 MBaud in an S7–400H or S7–400FH when a DP/PA or Y link is connected
(IM157, order number 6ES7157-0AA00-0XA0, 6ES7157-0AA80-0XA0, 6ES7157-0AA81-
0XA0). Remedy: see FAQ 11168943 in
Service & Support (http://www.siemens.com/automation/service&support)
262
time)
Note: The bus load is at its peak during restart of the DP master, for example, following
Power OFF/ON
System Manual, 03/2012, A5E00267695-11
S7-400H