Download DB to device without re-initalization

Description

To enable the subsequent editing of PLC programs that have already been commissioned and are running without error on a system, CPUs of the S7-1200 V4 and higher and S7-1500 series support the option of extending the interfaces of function or data blocks during runtime.

You can download the modified blocks without setting the CPU to STOP and without affecting the values of already loaded tags.

This is a simple means of implementing program changes. This load process (download without reinitialization) will not have a negative impact on the controlled process.

Principle of operation

In principle, every function or data block has a memory reserve by default, which can be used for subsequent interface changes. The memory reserve is not used initially. Activate the memory reserve if you decide on loading interface changes after having compiled and downloaded the block. All tags that you subsequently declare will be saved to the memory reserve. A subsequent download has no impact on the values of tags that have already been loaded.

If you decide to revise your program at a later time while the plant is not in operation, you also have the option of resetting the memory layout of one or more blocks in one step. With this action, you move all tags from the reserve area to the regular area. The memory reserve is now cleared and made available for further interface extensions.

Requirements

This "Download without reinitialization" function is available if the following requirements are met:

• The project is in the "TIA Portal V12" format or a higher version.

• You are working with a CPU of the S7-1200 V4 or higher or S7-1500 series.

• The blocks were created in LAD, FBD, STL, or SCL.

• The blocks were created by the user, i.e. they were not included in your delivery package.

• They are blocks with "optimized access".

Basic steps

Perform the following steps if you want to extend the interface of a function or data block and then load the block without reinitialization. A detailed description of the individual steps can be found in the following chapters:

1. By default, all blocks have a memory reserve of 100 bytes in the non-retentive memory. If needed, you can adjust the amount of memory reserve or define additional memory reserve in the retentive memory.

2. Activate the memory reserve.

3. Extend the block interface.

4. Compile the block.

5. Download the block to the CPU as usual.

Overview of settings for memory reserve

The overview of the project tree shows the settings for memory reserve for all program blocks at a glance:

To display the overview, follow these steps:

1. Select the "Program blocks" folder in the project tree.

2. Click "Maximizes/minimizes the Overview".