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Rockwell Automation Publication 2080-UM002N-EN-E - November 2022
Chapter 7 Program Execution in Micro800
Memory Allocation
Depending on base size, available memory on Micro800 controllers are shown in the table
below.
These specifications for instruction and data size are typical numbers. When a project is
created for Micro800, memory is dynamically allocated as either program or data memory at
build time. This means that program size can exceed the published specifications if data size
is sacrificed and vice versa. This flexibility allows maximum usage of execution memory. In
addition to the user-defined variables, data memory also includes any constants and
temporary variables generated by the compiler at build time.
If your project is larger, it affects the power up time. Typical power up time is 10...15 seconds
for all controllers. However, if your project has a lot of initial and project values, it may cause
the power up time to exceed 30 seconds. After boot up, EtherNet/IP connections may take up
to 60 seconds to establish.
The Micro800 controllers also have project memory, which stores a copy of the entire
downloaded project (including comments), as well as configuration memory for storing plug-in
setup information, and so on.
Guidelines and Limitations
for Advanced Users
Here are some guidelines and limitations to consider when programming a Micro800 controller
using Connected Components Workbench software:
• Each program/POU can use up to 64 Kb of internal address space. For all controllers
except Micro870, it is recommended that you split large programs into smaller
programs to improve code readability, simplify debugging and maintenance tasks.
• A User Defined Function (UDF) uses significantly less memory than a User Defined
Function Block (UDFB). For example, 30% less for a typical sized program compared to
a UDFB with one instance. The savings increases as the number of UDFB instances
increases.
• A User Defined Function Block (UDFB) can be executed within another UDFB, with a limit
of five nested UDFBs. Avoid creating UDFBs with references to other UDFBs, as
executing these UDFBs too many times may result in a compile error. This also applies
to UDFs.
Memory Allocation for Micro800 Controllers
Attribute
10/16-point
(Micro830)
20-point
(Micro820)
24- and 48-points
(Mico830, Micro850)
24-point (Micro870)
Program steps
(1)
(1) Estimated Program and Data size are “typical” – program steps and variables are created dynamically.
1 Program Step = 12 data bytes.
4 K
10 K
10 K
20 K
Data bytes
8 KB
20 KB
20 KB
40 KB