Specifications

Allen-Bradley ControlLogix Ethernet Driver Help

Performance Optimizations

Although the Allen-Bradley ControlLogix Ethernet Driver is fast, a few guidelines may be applied to optimize the

application and gain maximum performance.

For more information on optimization at the communication and application levels, select a link from the list

below.

Optimizing Your Communications

Optimizing Your Application

Performance Statistics and Tuning

Performance Tuning Example

Optimizing Communications

As with any programmable controller, there are a variety of ways to enhance the performance and system

communications.

Protocol Mode

The Protocol Mode determines how Logix tag data is accessed from the controller. There are three types of

protocol modes: Symbolic, Logical Non-Blocking and Logical Blocking. Descriptions are as follows:

l Symbolic Mode: Each client/server tag address is represented in the packet by its ASCII character

name.

l Logical Non-Blocking Mode: Each client/server tag is represented by its logical memory address in the

PLC.

l Logical Blocking Mode: The Logix tag is accessed as a single chunk of data. Each client/server tag

(such as MYTIMER.ACC) has a corresponding Logix tag (MYTIMER). Many client/server tags can belong to

the same Logix tag, as in the case of structures. On every read cycle, the Logix tag is read, its block is

updated in the driver cache and all client/server tags are updated from this cache.

Logical Non-Blocking Mode is generally recommended because it is the most efficient mode for gathering and

processing Logix tag data. Symbolic Mode is recommended for backward compatibility, whereas Logical Non-

Blocking Mode is recommended for projects containing a small number of references to UDT and/or predefined

structure Logix tags. Although Logical Blocking Mode can be efficient, it can also hurt performance if used

incorrectly. For more information on each mode's benefits and detriments, refer to Choosing a Protocol Mode.