Beginning with the SIXNET I/O Tool Kit version 3.0, SIXNET tag names can potentially be up to 73 characters in length (an eight character prefix, separator, and 64 character I/O Tag Name). The standard prefix separator character is a period. Only alphanumeric characters, "_" and "." are allowed in tag names.
The maximum allowable length of your tag names will depend on the capabilities of the hardware and software you will be using. By default, tag names are restricted to 16 characters to be compatible with ISaGRAF v3.##. If you are using IPm-based stations with version 3.4 or newer firmware and you are not using ISaGRAF, the tag name restrictions can possibly be changed in the Tag Restrictions window of the SIXNET I/O Tool Kit to suit your other applications. We strongly suggest you check the documentation for each of your other application programs to find out what the program’s restrictions are. Here are some known tag name limits for SIXNET hardware and third party software:
Hardware:
IPm firmware version 3.4 or higher 64 characters
IPm firmware prior to version 3.4 20 characters
All other SIXNET stations 16 characters
Software:
DNP3 configuration utility 40 characters
AGA configuration utility 40 characters
Kepserver (Modbus OPC server) 32 characters
KepServerEx (SIXNET OPC server) 64 characters
Citect 6.1 w/SxDirect driver 64 characters
Citect w/IOmap driver 16 characters
ISaGRAF v3.## 16 characters
ISaGRAF v5.# (future software) 64 characters
Notes:
1. The optional exporting functions in the SIXNET I/O Tool Kit will export your tag names at their full length, up to 64 characters in the I/O tag name portion of each tag name. Therefore, it is important that you limit your tag names to a length that is compatible with the maximum tag name length allowed by the most restricted third party software program you will be exporting tag names to. When exporting to an OPC server, you should consider the capabilities of the OPC client(s) you will be using. If you are using ISaGRAF, you should restrict the tag name length to 16 characters.
2. If your application does not allow '.' characters, then specify tag names with '_' as a prefix separator. The IOmap will accept and check for this alternative. In large I/O systems, lookups of tag names may be slower.
Truncating tag names is not recommended because users commonly append numbers on the end of tag names to sequentially name registers.
Sample Tag Names:
start_switch
Zone Temp 1
Zone_Temp_1
Sample Tag Names with station prefixes:
UNIT1.start_switch
S11.start_switch
S11_start_switch