Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 213)

Appendix
A.1 Information about upgrading to a CPU 31xC or CPU 31x
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
A-7
A.1.8 Using consistent data areas in the process image of a DP slave system
Consistent data
The table below illustrates the points to consider with respect to communication in a DP
master system if you want to transfer I/O areas with "Total length" consistency. You can
transfer a maximum of 128 bytes of consistent data.
Table A-1 Consistent data
CPU 315-2 DP
(as of firmware 2.0.0),
CPU 317,
CPU 31xC CPU 315-2 DP
(as of firmware 1.0.0),
CPU 316-2 DP,
CPU 318-2 DP (firmware < 3.0) CPU 318-2 DP
(firmware >= 3.0)
Even if they exist in the process
image, consistent data is not
automatically updated.
You can choose whether or not
to update the address area of
consistent data in the process
image.
The address area of consistent
data in the process image is
automatically updated.
To read and write consistent
data, you can also use SFC 14
and SFC 15. If the address area
of consistent data is not in the
process image, you must use
SFC 14 and SFC 15 to read
and write consistent data.
Direct access to consistent
areas is also possible (e.g.
L PEW or T PAW).
To read and write consistent data,
you must use SFC14 and 15.
To read and write consistent
data, you can also use SFC 14
and SFC 15.
If the address area of
consistent data is not in the
process image, you must use
SFC 14 and SFC 15 to read
and write consistent data.
Direct access to consistent
areas is also possible (for
example, L PEW or T PAW).