When you upgrade your S7-1200 CPU with firmware V2, after downloading from STEP 7 (TIA Portal) the CPU does a warm restart the first time a change is made to RUN mode. A warm restart does not cause the data in the DBs and the monitoring values to be overwritten with the start values.
S7-1200 CPU modules that still have firmware version V1, are put into STOP mode when downloading from STEP 7 (TIA Portal) even if you are downloading just one block. When the change is then made to RUN mode, the cold start of the CPU deletes all the memory areas including the remanent memory areas and in the data blocks the monitored values are overwritten with the start values.
In this way, with the S7-1200 as from firmware V2 you have the option of downloading the changed data blocks to the CPU without the CPU going into STOP. Only if you put the CPU into STOP and then into RUN mode again will the monitoring values in the main memory be overwritten with the start values. Alternatively you can also overwrite the monitoring values by means of the monitoring table.
However, please note the two cases in which your CPU with firmware V2 nevertheless performs a cold start:
- When you download the project from STEP 7 V10.5 into a CPU with firmware V2.
- When you download your program in STEP 7 (TIA Portal) into a CPU with firmware V2, but you have a CPU with V1 configured in the device configuration.
The table below shows the differences between the S7-1200 and the S7-300/400 modules when you download data blocks from a CPU.
|Storage of the start values with which a DB was downloaded into the CPU
||In the load memory
||In the load memory|
(values can no longer be read back from the load memory)
|After download from the CPU
||Start values are transferred back again from the load memory into the offline DB
||The current monitored values are downloaded from the CPU and transferred to the "Start values" column in the offline DB.|
You can use the monitored values that the tags are currently capturing in the CPU as start values in the data block. Refer to the information in the STEP 7 (TIA Portal) Online Help under:
- "Use monitored values as start values"
- "Download blocks to device in RUN mode (S7-1200/1500)"
- "Download blocks to device in RUN mode (S7-300/400)"