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are written via the EtherNet/IP “data table write” service. Different tags exist for reading vs. writing.

Any given register can be accessed with its own unique tag name, or an array tag can be used to access a group of registers with one PLC instruction. Tag names are generated according to the following structure:

[action prefix][_reg_][register number]

Where

[action prefix] is a 2-character field, and is equal to either “rd” for read tags, or “wr” for write tags. Although commonly followed for naming clarity, this “read vs. write” naming convention is not strictly enforced by the interface card, however: it is perfectly acceptable to write to a tag that starts with “rd” and read from a tag that starts with “wr”.

[_reg_] is just the 5-character sequence “_reg_”.

[register number] is a 1- to 4-character field (“1”, “2”…”1484”, “1485”) corresponding to the referenced register number.

Examples

 

Read “acceleration time 1” (register #10) ...................................

rd_reg_10

Write “option frequency command” (register #1008) ..................

wr_reg_1008

Read “inverter status 1” (register #1402)....................................

rd_reg_1402

Additionally, a few special tags exist which provide backward-compatibility with V1.000 network interface CPU firmware. These are specified in Table 4.

Table 4: Special Tag Reference

Service

Tag Name

Register Start

Same As…

Data table read

rd_reg_basic

1

rd_reg_1

Data table read

rd_freq_out

1401

rd_reg_1401

Data table read

rd_inv_stat1

1402

rd_reg_1402

Data table read

rd_torq_out

1419

rd_reg_1419

Data table read

rd_inv_stat2

1443

rd_reg_1443

Data table write

wr_reg_basic

1

wr_reg_1

Data table write

wr_cmd1

1007

wr_reg_1007

Data table write

wr_freq_cmd

1008

wr_reg_1008

Data table write

wr_cmd2

1024

wr_reg_1024

Data table write

wr_torq_cmd

1034

wr_reg_1034

To read data from the interface card, the application PLC program must reference a “source element” from which to start reading and the “number of elements” to read. The “source element” will be a tag name constructed according to the naming convention shown above, or a special tag as shown in Table 4. The “source element” can be either a base tag (such as “rd_reg_1301”, which starts at register 1301), or an offset from a base tag (such

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