Demo3D.PLC.Comms Namespace

The Demo3D.PLC.Comms namespace provides a set of built-in Demo3D communication protocols.

Classes

	Class	Description
	AccessParameters	Parameters for accessing a PLC tag or memory address.
	Alignment	Directs field memory layout / alignment.
	AlignmentPacked	A class to help with sequential field memory layout / alignment. Aligns bits on bit boundaries, and all else on byte boundaries.
	AlignmentSequential	A class to help with sequential field memory layout / alignment.
	AlignmentSequential16	A class to help with sequential field memory layout / alignment. Aligns bits and bytes on their respective boundaries, and larger types on 16-bit boundaries.
	AlignmentSequential32	A class to help with sequential field memory layout / alignment. Aligns bits, bytes, and Int16 on their respective boundaries, and larger types on 32-bit boundaries.
	AlignmentSequential64	A class to help with sequential field memory layout / alignment. Aligns bits, bytes, Int16 and Int32 on their respective boundaries, and larger types on 64-bit boundaries.
	BrowseItemBase	Base implmentation of IBrowseItem.
	BrowseItemBranch	A base class for implementing a symbol table branch.
	BrowseItemExtensions	Extension methods for IBrowseItem.
	BufferMarshallerT	A class for marshalling/unmarshalling objects into memory.
	ConnectionPointContainerExtensions	IConnectionPointContainer extensions.
	ConversionFunction	A conversion function returned from GetConvertFrom(IDataContextProvider, DataType, DataType) or GetConvertTo(IDataContextProvider, DataType, DataType).
	DataArrayT	A data array.
	DataContextProvider	Provides extensions to IDataContextProvider.
	DataConverter	Provides a unified way of converting types of values to other types.
	DataConverterAttribute	Specifies what type to use as a converter for the object this attribute is bound to.
	DataStruct	A dynamic data structure.
	DataType	Describes a data type, either a .Net System.Type or dynamic type that may have no .Net Type equivalent.
	DataTypeBuilder	Dynamic structure builder.
	DataTypeFieldItem	A field definition for the dynamic structure builder (see DataTypeBuilder).
	DataTypeMemoryLayout	Returns the field offset and size for fields of a structure. (Describes just one element for an array type.)
	FieldDescriptor	One field of a structure.
	FieldOffsetBitsAttribute	Specifies the offset into a structure of a field (in bits).
	FieldSizeBitsAttribute	Specifies the size of a field (in bits).
	MemoryAddress	A memory address.
	MemoryAddressMemoryAddressConverterAddressType	A base data type converter.
	MemorySymbolTableAddressType	A class for constructing symbol tables for servers that are primarily accessed with memory addresses.
	MessageContextBase	Optional information about a request received.
	MetaProperties	Non-standard properties.
	MetaPropertyDatabase	Database of non-standard properties.
	MetaPropertyDescriptor	Description of a non-standard property.
	StringAddress	An address that supports a string representation.
	TypedMemoryAddress	A strongly typed PLC specific memory address.
	VectoredRequest	A vectored request.
	VectoredRequests	A vector of requests which can be executed multiple times.

Structures

	Structure	Description
	AddressArea	Describes an addressable area within an address space.
	DataArrayTIndexRange	Index range of elements that changed.
	DataArrayTValueChange	Previous value of an element that changed.
	DataDimension	One array.
	DataValue	A data value.
	DataValueT	A strongly-typed timestamped data value.

Interfaces

	Interface	Description
	IAddress	An address of some sort.
	IAddressSpace	Memory address space identifier.
	IAddressTranslatorService	Translator service for mapping from one IAddress to another IAddress.
	IBrowseItem	A browsable item, usually representing a symbol in the PLC symbol table. Can optionally also implement IBrowseItemDescription.
	IBrowseItemDescription	Extensions to the core IBrowseItem to provide more detail.
	IConnectionPoint	A single connection point.
	IConnectionPointContainer	A custom object that contains connection points. Add this as an aspect on a visual to make the visual appear in the loopback tag server.
	IDataContextProvider	Provides contextual information for a data conversion using DataConverter.
	IDataRefreshService	Connections created through the IO browser will always try to refresh cached data on model connection or reset. This is essential for PLC protocol implementations, as it ensures that there are no data discrepancies between the PLC and the model. This causes issues for protocols that don't always need this functionality, such as stateless protocols where data exchanges are processed in isolation. This service allows protocol implementations to have control over this functionality.
	IListExt	Extensions to IList.
	IModifySymbolTable	An interface for modifying a symbol table.
	INotifySymbolTable	Notifies when the symbol table changes.
	IOffloadingService	A protocol that implements this service agrees to offload write requests.
	ISymbolTable	An interface for providing access to a symbol table.
	ISynchronizedIOService	A service for controlling when IO occurs.

Delegates

	Delegate	Description
	ConversionDelegate	Conversion function.
	IOAsyncDelegateT	Delegate for IO with the peer.
	IOBeforeHandler	Delegate to execute before an IO event.
	IOErrorHandler	Delegate for notifying an error.
	IOSuccessHandler	Delegate for indicating IO success.

Enumerations

	Enumeration	Description
	AccessRights	Whether a data item can be read or written.
	BrowseFlags	Browse control flags.
	BrowseItemBaseSearchFlags	Search control flags.
	CanModifySymbolFlags	Flags describing how a symbol can be modified.
	CanReadSymbolsFlags	Flags describing whether and how to read the symbol table.
	DataTypeConvertibleFlags	Flags for specifying acceptable conversions.
	IOControl	Cache and IO control flags.
	PlcFlags	Flags specific to PLC connections.

Remarks

Support for server connectivity is broadly split between Tag and Memory servers; reflecting the primary concepts that the server exposes for accessing its data.

Tag

Tag-based servers expose PLC data-points as explicit tags. They tend first to expose their symbol table detailing all the tags that the client can access, and then offer some API or protocol for the client to access tags. Examples include EtherNet/IP CIP Class 3, OPC (UA and DA), and BR Automation PVI.

See Demo3D.PLC.Comms.Builtin for an example implementation of a tag server.

Memory

Memory-based servers expose raw PLC memory, allowing the client (Demo3D) to read and write bytes of data direct to/from the memory in the PLC. Examples include Modbus, Siemens S7 Functions, and Beckhoff TwinCAT ADS. These servers may also expose a symbol table, where the symbols in the table are just a mapping from symbol name to memory address, and the underlying access is still directly to memory in the PLC.

See Demo3D.PLC.Comms.Builtin for an example implementation of a memory server.

List of services:

Access	Interface	Description
Common	IAddressTranslatorService	A service for translating one address to another.
	ISymbolTable	Provides access to a symbol table.
	INotifySymbolTable	Provides access to a symbol table, and notifies when the symbol table changes.
	ISynchronizedIOService	Controls when IO occurs.
	IOffloadingService	A protocol that agrees to offload write requests..
Direct Tag	IDirectTagAccessService	Simplified tag client interface.
	INotifyDirectTagAccessService	Simplified tag client interface for a peer that will notify when tag values change.
Tag	ITagService	Provides tag access to the peer.
	IDirectTagService	Provides direct tag access to the peer, bypassing any caches.
	INotifyTagService	Provided cached access to tags in a peer that will notify when tag values change.
Direct Memory	IDirectMemoryAccessService	Simplified memory client interface.
	INotifyDirectMemoryAccessService	Simplified memory client interface to a peer that will notify when memory changes.
Memory	IMemoryService	Provides access to memory in the peer.
Memory	IMemoryPartitioningService	Controls access to memory in the peer.
	IDirectMemoryService	Provides direct access to memory in the peer, bypassing any caches.
	INotifyMemoryService	Provides access to the memory in a peer that will notify when the data at the address changes.