The following variables and modules, while frequently found in communication drivers, are defined as optional. Of particular note in this list is VTSMaxBlock. While used by nearly every communication driver, it is defined as an optional component.
• Hold - Set to 1 to hold data on error. Otherwise, all data is invalidated when an error occurs.
• VTSMaxBlock - defines the maximum size for block reads and writes
• ByteOrder - reverse byte order if data is not being provided in the Intel, little-endian format. By default, VTS assumes that the 1st byte is the low-order byte.
• RPCService - necessary for networked applications. Set to a string that is the name of the RPC service that will handle the driver. Usually, the service name will be the same as the tag name. There is also a config.ini setting for this value.
• GetClientRevision - RPC service
• GetClientChanges - RPC service
• CoalesceRPC - If true, ensures that all data packets will be sent to client machines. See RPC Queuing of Data Packets.
• CommStatsUpdateRate - For this and the next two items, see: Driver Diagnostic Tools.
• CommStatsQualityFactor -
• DisableCommStats -
• Root - set to some object value (usually Self()