Siemens SIMATIC FC 45 Function Manual page 107

Parameterizing process image mode
Note
Process image mode does not use the FB 45. This section describes how to handle and
program the process image mode. Only fixed-code MDSs of type "MDS F1xx" can be read in
this mode.
Process image mode is parameterized in HW Config by selecting the appropriate entry from
the GSD file. Process image mode does not offer functions for the application.
Figure A-8
Process image mode: Operating principle
After the ASM and PROFIBUS have powered up, code 00 00 00 00 00 is stored in the
process image for each MDS. Each SLA channel immediately starts to scan its surroundings
for a new MDS no. As soon as the MDS no. has been read, the process image indicates the
fixed-code information. The new MDS no. is retained until an MDS with a new no. is read.
The new MDS overwrites the old number. The data must be read to a data block with SFC
14 to ensure that the number is always transferred consistently with PROFIBUS or is
indicated on the S7. In addition to the 5 bytes of fixed-code information, status information is
located in the 1st byte of the process image which the user can evaluate.
FC 45
Function manual, Release 03/2006 , J31069-D0167-U001-A2-7618
Selecting process image mode for ASM 854/850 based on the number of channels
Brief description of ASM hardware
A.6 ASM 854
A-25