Before the introduction of the Namespace, the prefix used to identify world-wide uniquely a certain library. With the conversion from CODESYS V2 to V3 the prefix was substituted by the namespace. However it was not possible to change all of the already existing libraries as for instance this would have resulted in terms like SysFile.SysFileClose which are not very convenient to work with. Therefore you can still find prefixes in stead of namespaces in CODESYS libraries.
In contrast to the namespace the prefix is not separated from the symbol by a full stop (e.g. CAA.Handle) but either by an underscore (e.g. MBM_GetBlock) or by nothing at all (e.g. SysFileClose).
|
General Structure |
Example |
|---|---|
|
<namespace>.<symbol> |
CAA.Handle |
|
<prefix>_<symbol> |
MBM_GetBlock |
|
<prefix><symbol> |
SysFileClose |
The namespace, together with the Placeholder, must be registered at 3S via an informal email to libregistry@codesys.com.
With each CODESYS setup also the file LibraryRegistry.chm is delivered. There the currently registered namespaces and placeholders are listed.
The namespace of a library can be changed in the context of an library manager. But the name of a placeholder can not be changed and therefore it is highly recommended to register it. So that each Common library can can be referenced by a unique placeholder name.