Varec TankGate Interface 8315 Series - Manual (Page 36)

Software Description Tank Gate Interface
26 Installation and Operations Manual
4.3.5 Fixed Modbus Map
For each version of the Tank Gate Interface, there is a fixed map of data registers. A partial
example is shown below:
Table 4-1: Fixed map of data registers
4.3.6 GWBLK method
The GWBLK is the preferred means to address data in the Tank Gate Interface. The GWBLK has a
great deal of flexibility. Data can be scaled, or grouped using the GWBLK. The Gateway Block
(GWBLK) allows the user to specify data address and point reference combinations. This allows
the Tank Gate Interface to be used with an existing system that is already configured. The Tank
Gate Interface can be tailored to meet the needs of the Host. In some cases, the Host system
may have some constraints in the use of its Modbus scanner that make it necessary to use a
GWBLK. In this mode, the user defines a GWBLK point and specifies which database parameter
will correspond to a particular data address. When a request from a master is received, the
Modbus Slave protocol handler will first search for any GWBLK points and determine if the data
address of the request is specified in one of the GWBLK points. If the data address is contained
in a GWBLK point, then the corresponding point reference is used to provide the data for the
reply to the master. If the data address is not in any GWBLK point, then data will be read using
the prevailing Address Mode.
The Gateway Block (GWBLK) allows the user to specify data address and point reference
combinations. The GWBLK acts as a lookup table for data items in the Tank Gate Interface. The
user defines a GWBLK point and specifies which database parameter will correspond to a
particular data address. When a request from a master is received, the Modbus Slave protocol
handler will search for any GWBLK points and determine if the data address of the request is
specified in one of the GWBLK points. If the data address is contained in a GWBLK point, then
the corresponding point reference is used to provide the data for the reply to the master.
The procedure for using the GWBLK is given below:
•
Add a GWBLK point. Depending upon the addressing requirements of the host system, it
may be necessary to add additional GWBLKs.
•
Configure the GWBLK by setting the Address, PntRef and Size parameters to the parameters
of interest in the Tank Gate Interface. Refer to the following examples:
Address Type Number Parameter Data Type
5000 MSTX 0 Command CODED
5001 MSTX 0 Level REAL
5003 MSTX 0 Temp REAL
5005 MSTX 0 Value REAL
5007 MSTX 0 Status HEX
5008 MSTX 0 PntStatus IHEX
5009 MSTX 0 Elapse TIME
5011 MSTX 1 Command CODED
5012 MSTX 1 Level REAL
5014 MSTX 1 Temp REAL
5016 MSTX 1 Value REAL
5018 MSTX 1 Status HEX
5019 MSTX 1 PntStatus IHEX
5020 MSTX 1 Elapse TIME