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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
