Siemens Simatic S7-400

Cycle and Response Times of the S7-400
9.2 Cycle Time Calculation
S7-400 Automation System, CPU Specifications
9-4 Manual, 10/2006, 6ES7498-8AA04-8BA0
Process Image Updating
The table below shows the CPU times for process image updating (process image transfer
time). The times listed in the table are "ideal values" that may be increased by the
occurrence of interrupts and by CPU communications.
The transfer time for process image updating is calculated as follows
C + portion in central controller (from row A of the following table)
+ portion in the expansion rack with local connection (from row B)
+ portion in the expansion rack with remote connection (from row C)
+ portion over integrated DP interface (from row D)
+ portion of consistent data over integrated DP interface (from row E1)
+ portion of consistent data over external DP interface (from row E2)
__________________________________________________________________
= Transfer time for the process image update
The tables below show the individual portions of the transfer time process image updating
(process image transfer time). The times listed in the table are "ideal values" that may be
increased by the occurrence of interrupts and by CPU communications.
Table 9-3 Portions of the process image transfer time
Portions CPU 414 CPU 416
n = number of bytes in the process image
C Base load 7 µs 5 µs
O In the central rack
*)
n * 1.8 µs n * 1.75 µs
B In the expansion rack with local connection
*)
n * 5.5 µs n * 5.4 µs
C In the expansion rack with remote connection
*) **)
Reading
Writing
n * 12 µs
n * 11 µs
n * 12 µs
n * 11 µs
D
1
In the DP area for the integrated DP interface n * 0.5 µs n * 0.45 µs
D
2
In the DP area for the external DP interface
CP 443-5 extended
n * 2.5 µs n * 2.4 µs
E
1
Consistent data in the process image for the
integrated DP interface
n * 0.45 µs n * 0.3 µs
E
2
Consistent data in the process image for the external
DP interface (CP 443-5 extended)
n * 2.0 µs n * 2.0 µs
F
1
In the PN/IO area for the integrated interface n * 5.6 µs n * 5.6 µs
F
2
In the PN/IO area for the external interface
CP 443-1 EX 41
n * 3.1 µs n * 2.8 µs
*
In the case of I/O modules that are plugged into the central rack or an expansion rack,
the specified value contains the runtime of the I/O module
**
Measured with the IM 460-3 and IM 461-3 with a connection length of 100 m