Varec 8315 Series Size Parameter, Addr1 is the Data Address and PntRef1 is the corresponding

8315 L&J Tankway Software Description		TankGate Interface
	Configuration Parameters	Function
	Addr1	Addr1 is the Data Address and PntRef1 is the corresponding
	PntRef1	database parameter that will be used for a response. The default
	Size1	Size is 1. See the discussion below for more detail on the Size
	Filter1
	Addr10	parameter.
	PntRef10	The Filter is used to determine if the data is valid. The PntStatus of
	Size10	the point specified by the PntRef is read and if there are bits set
	Filter10
		that match the Filter, the source data is considered invalid. The
		output registers will be set to the value determined by the
		CommFailValue.
	Dynamic Parameters	Function
	PntStatus	Byte value indicating status of point Values are:
		0: No error
	PntCheckSum	CRC-16 Checksum of point's static Configuration Parameters

4.12.2Application

The GWBLK point is a look-up table used by the Modbus Slave protocol handler. Up to sixteen address-point reference pairs may be used per GWBLK point. Multiple GWBLK points may be used if necessary. The Addr parameter specifies the data address. The corresponding PntRef parameter specifies the database parameter for the request. The Gateway Block point allows the user to use the TankGate easily in retro-fit applications. It is not necessary to re-configure an existing HMI or Host system. The user can configure the TankGate to match the addresses used in the Host system.

When the Modbus Slave protocol handler receives a request, it searches the GWBLK points to determine if any of the Addr parameters match the request. If a match is found, the data referenced by the PntRef parameter will be used for the response.

There are three data modes: DataMode=0, which returns the data in the default format, and DataMode=1, which returns the data in an integer format. DataMode=1 will scale IEEE floating point data to an integer value, using the Offset, Scale, ValueMin and ValueMax parameters. If DataMode = 4, the data wil be scaled to an integer by multiplying the data value times the Scale parameter.

The DataMode can also control if the data is changed to 0xFFFF if the data is invalid. The Filter parameter is compared to the PntStatus of the PntRef parameter. If bits in the PntStatus match bits in the Filter, the data is considered invalid and the a read from a modbus host will result in the data being set to 0xFFFF.

When Block Read or Write requests are received, then the way in which the Modbus Slave protocol handler responds is determined by the Size parameter.

4.12.3Size Parameter

A range of addresses can be specified by setting the Size parameter. This sets the indexing mode to Number Indexing, which means that Block Read/Write requests from the Hosts are handled by stepping through the points number by number. For example, if Addr1 is 100, and PntRef1 is WV1900.00.RawValue, then a Block Read to address 100 with a length of 8 will return the values, WV1900.00.RawValue, WV1900.01.RawValue, .. WV1900.07.RawValue. Setting the Size to 1 does not limit the read to 1 parameter, rather it indicates that block operations will be processed by stepping through points by incrementing the number, starting with parameter specified by the PntRef.

46 Installation and Operations Manual