Siemens S7-300 appendix Recipes, Introduction, Processing sequence, Recipe Recipe n

Memory concept 4.2 Memory functions

4.2.5Recipes

Introduction

A recipe represents a collection of user data. You can implement a simple recipe concept using static DBs. In this case, the recipes should have the same structure (length). One DB should exist per recipe.

Processing sequence

Recipe is written to load memory:

•The various data records of recipes are created as static DBs in STEP 7 and then downloaded to the CPU. Therefore, recipes only use load memory, rather than RAM.

Working with recipe data:

•SFC83 "READ_DBL" is called in the user program to copy the data record of a current recipe from the DB in load memory to a static DB that is located in work memory. As a result, the RAM only has to accommodate the data of one record. The user program can now access data of the current recipe. The figure below shows how to handle recipe data:

Loading memory

(MMC)

Recipe 1

Recipe 2

:

Recipe n

Saving a modified recipe:

SFC 83 READ_DBL

SFC 84 WRIT_DBL

Working memory

(CPU)

Current

recipe

•The data of new or modified recipe data records generated during program execution can be written to load memory. To do this, call SFC 84 "WRIT_DBL" in the user program. These data written to load memory are portable and also retentive on memory reset. You can backup modified records (recipes) by uploading and saving these in a single block to the PG/PC.

Note

Active system functions SFC82 to 84 (active access to the MMC) have a distinct influence on PG functions (for example, block status, variable status, download block, upload, open). This typically reduces performance (compared to passive system functions) by the factor 10.

CPU 31xC and CPU 31x, Technical data	4-15
Manual, Edition 08/2004, A5E00105475-05