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Term Protocol Mode

Definition

The means by which Controller Tag addresses are specified in data access communication packets.

Default Type

Due to the symbolic nature of Logix Tag-Based Addressing, tags can be of any data type. This is in contrast to DF1 where file access (such as N7:0) is always a given set of data types (Word, Short). Because of this flexibility, there needs to be a data type that tags default to when no data type is explicitly set. This is the case when a tag is created in a client and assigned the data type "Native" or created in the server and assigned the data type "Default". In these cases, the tag in question will be assigned the data type set as the Default Type. There are also cases in Automatic Tag Database Generation where the Default Type is used to set a server tag's data type.

Gateway

Utilizing an EtherNet/IP communication module to obtain access to a DH+ or ControlNet network from the same backplane. Rack must contain an EtherNet/IP communication module and a DHRIO or CNB module.

Link Address

Unique identifier for an interface module (such as Node ID, IP address and so forth).

Packet

Stream of data bytes on the wire representing the request(s) being made. Packets are limited in size.

Logical Mode

A Protocol Mode in which Controller Tag addresses are specified by their logical address in the controller. This provides a performance increase over Symbolic Mode but requires a project upload to gather the logical addresses. There are two logical addresses that can be used. If the controller revision is V20 or lower, the logical address is the Physical (DMA) address. If the controller revision is V21 or higher, the logical address is the Symbol Instance ID.

*For more information on tag division, refer to Performance Statistics and Tuning and Optimizing Your Communications.

Logix Tag-Based Addressing

Term Array Element

Definition

Element within a Logix Array. For client/server access, the element must be an atomic. For example, ARRAYTAG [0].

Array with Offset

Client/Server Array Tag whose address has an Array Element specified. For example, ARRAYTAG [0] {5}.

Array w/o Offset

Client/Server Array Tag whose address has no Array Element specified. For example, ARRAYTAG {5}.

Atomic Data Type

A Logix, pre-defined, non-structured data type. Example: SINT, DINT.

Allen-Bradley ControlLogix Ethernet Driver Help

Non-Blocking: Each Client/Server Tag is requested individually from the device. Similar to Symbolic in nature but much faster in performance.

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Glossary

Routing Symbolic Mode

Utilizing one or more Logix racks to hop to another Logix rack.

A Protocol Mode in which Controller Tag addresses are specified by their ASCII character equivalent. Each Client/Server Tag is requested individually. This provides immediate access to controller data without a project upload but is overall slower in performance when compared to any of the Logical Modes. When the Default Data Type is set to Default, the tag data types will be returned from the controller during automatic tag database generation.

Tag Division

Special assignment of tags to devices whose Protocol Mode is set for Logical Blocking or Logical Non-Blocking Mode. Assignment is based on rules that maximize the performance of access to these tags.*

Blocking: Each Controller Tag is requested as a single block of data. Each Client/Server Tag is updated via cache storage of this data in the server. Much faster performance over Symbolic Mode.

Port ID Project Synchronization

Specifies a way out of the interface module in question (such as channel).

Synchronization of the driver's project image with that of the controller project. This is required for the Logical Protocol modes.

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