Optimized Block Access; Introduction - Siemens SIMATIC S7-1500 Getting Started

3.2.8

Optimized block access

3.2.8.1

Introduction

Operating principle
The "optimized data blocks" of the CPUs of the S7-1500 series are optimized for
performance and are only programmed symbolically. By using the optimized data blocks,
you make your program more efficient, because the declared tags are given symbolic names
and no longer a fixed address.
You can create data blocks with any structure without paying attention to the physical
arrangement of the individual tags. Quick access to the optimized data is always available
because the data storage is optimized and managed by the system.
Changing data types increases the risk of error in the standard block. In the optimized block,
changes lead to a reorganization of the data storage. Addressing remains unique.
To enable the subsequent editing of user programs that are already running in a CPU, the
S7-1500 CPUs 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 actual values of tags already loaded.
In addition: You can define in the data block itself, which the values in the CPU are read-only
for an HMI device ("Visible in HMI") or which can be written ("Accessible from HMI").
S7-1500
Getting Started, 05/2014, A5E03981761-AC
Software section
3.2 Creating the program
59