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8315 L&J Tankway Software Description

TankGate Interface

46 

Installation and Operations Manual

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.

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.

Addr1

PntRef1

Size1

Filter1

Addr10

PntRef10

Size10

Filter10

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