Register Block Configuration

The register block configuration defines which data blocks are to be read from the available PLC stations. Each station must have at least one register block configured. The register blocks for the symax driver are listed in the plcreg.dbf database file:

Field Name	Title	Description
STATION	Station Name	The station name represents a controller on the network. The communications route is identified through a lookup based on the station name.
REGTYPE	Register Type	As the Symax protocol treats each PLC/device as a single contiguous memory segment, the register type field is effectively ignored at the driver implementation level. By convention the register type "R" is used. Another alternative is to leave the register type blank.
STARTADDR	Start Address	The start address of this register block in the destination PLC. The start address must fall within the valid address range of the destination device.
ENDADDR	End Address	The end address of this register block in the destination PLC. There is a limit of 128 registers for Symax read requests, so the total address range (end - start + 1 ) must not exceed a value of 128 registers for successful communications.
DESC	Description	A short description of the purpose of this register block. This field is purely for documentation purposes.
NSCANTIME	Normal Scan Time	The rate in seconds at which the driver attempts to update this register block when no MacroView processes require data from the block. It provides a means of allowing the shared memory register values to be reasonably up to date even immediately after a process indicates that it requires values from the register block. As soon as a register block has been placed in demand mode for a process, the demand scan time DSCANTIME will be in effect.
DSCANTIME	Demand Scan Time	The rate in seconds at which the driver attempts to update this register block when MacroView processes require data from the block. This value should be a higher rate than the NSCANTIME value and be set based on balancing the network throughput resources and the required end user update rates.
SCAN	Scan Flag	Determines whether this block should be included in the read request scheduling performed by the driver. As the symax driver does not support unsolicited message processing, this flag should always be set to true. Otherwise the register block would never be updated.