Varec 8300 series, Инструкция по установке и эксплуатации, Страница: 45 / 150

8303 Software Description
Varec, Inc. 35
Application
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 you
to use the 8300 series Tank Gate Interface easily in retrofit applications. It is not necessary to
re-configure an existing HMI or Host system. You can configure the 8300 series Tank Gate
Interface 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 will 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.
Size 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 MSTX.00.RawValue, then a Block Read to address 100 with a length of 8 will return
ValueMin Output range Offset used for scaling the output to an integer value when
DataMode=1.
ValueMax Output range Scale used for scaling the output to an integer value when
DataMode=1.
CommFailValue Value to set all of the output registers to when there is a communications
or other failure. The CommFailValue works in conjunction with the Filter
values. If the PntStatus of the PntRef has bits set that match the Filter, the
reference value is declared invalid and the output value will be set to the
CommFailValue. This mode is overridden by DataMode = 0x02.
Addr1-10
PntRef1-10
Size1-10
Filter1-10
Addr1 is the Data Address and PntRef1 is the corresponding database
parameter that will be used for a response. The default Size is 1. See the
discussion below for more detail on the Size parameter.
The Filter is used to determine if the data is valid. The PntStatus of the
point specified by the PntRef is read and if there are bits set 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
Configuration Parameters Function