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- Read Tag Service [0x4C]
- Write Tag Service [0x4D]
- Read Tag Fragmented Service [0x52]
- Write Tag Fragmented Service [0x53]
- Execute PCCC [0x4B] - communication with older SLC 5/05 and PLC5E, see the PCCC Max Data Length parameter
While browsing the proprietary Rockwell message Get Instance Attribute List [0x55] is used. Some devices or firmware versions do not support this message or the Symbol Object [0x6b] class that the message uses.
Symbolic name - a symbolic name. It can be simple (Test) or contain the address of a specific item of a one-dimensional array (Test [3]), multidimensional (Test [1] [2]), item of a structure (Test.MyItem1), or item of an array of structures (Test[2].MyItem1).Kotva symbolic_name symbolic_name
If the PCCC Max Data Length parameter is set to a non-zero value, the symbolic address of the I/O tag starts to be interpreted as an address in SLC-500 format - see Allen-Bradley CSP/PCCC protocol (e.g. N:3 or $T4:0/ACC). Other settings (Item count, Fragmented read) are unused. Reading fields into a structure and writing values are not supported either.
Item count - number of elements in the case of an array of values.This number may be less than or equal to the actual size of the array in the device.If it is not specified, one element is read.Kotva item_count item_count
Fragmented read - indicationthat the Read Tag Fragmented Service message should be used for reading because the entire array does not fit into a message with the length specified by the Max Packet Size parameter.
Note: If the reading using the Read Tag Service message returns an error code Partial Transfer [0x06], the next reads will use the Read Tag Fragmented Service message as if the Fragmented read indication was set.
By clicking the Browse button, a browse dialog can be opened and a list of symbolic names retrieved as long as the communication with the device is established. For each symbolic name, its type is also read. In the case of structures or arrays of structures, the type is identified as "STRUCTURE (---)". D2000 cannot presently use such complex types - it is necessary to specify an address of a particular item as a symbolic name (e.g. MyStruct.MyItem or MyArr [1] .MyItem).
The Auto option is used to set the NONE/AUTO attribute type (autodetect). If this option is off, the attribute type is copied to the I/O tag along with the symbolic name after double-click on a specific line in the list of symbolic names.
The Refresh button is used to repeatedly retrieve the list from the device. The KOM process caches a list of symbolic names, so the second and subsequent opening of the browse dialog is significantly faster than the first one during which the data is being read from the device.
Note: symbolic names beginning with the underscore are related to system objects of the Rockwell device, other names are user-defined.
Atribute type - the type the type of attribute. In the case of standard addressing, it is necessary to enter a specific type. In the case of symbolic addressing, it is possible to leave the type of the attribute as NONE/AUTO (autodetect), since proprietary Rockwell messages contain both the value and the attribute type. An exception is if the I/O tag is write-only - then the attribute type must be specified.
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Array index - index of an element in an array, if the attribute is an array. In the Ethernet/IP protocol, an array is indexed from zero, so if the Item count is equal to 3, indices 0, 1, and 2 are allowed.
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