Galvanic Applied Sciences 943-TGS, Operation Manual

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Revision 1 64 6/27/2017
Endian Swap and Register Swap are used to manipulate how the data is transmitted and
they only apply to Modicon Modbus data. In Modicon Modbus, floating point numbers are
transmitted in 2 16 bit words. Endian Swap determines if the most significant bit is transmitted
first or if the least significant bit is transmitted first for each word. Register swap determines if
the portion of the number before the decimal place is transmitted in the first word or if the
portion of the number after the decimal place is transmitted in the first word.
The various items on the Available points listing on the left side of the tab can be accessed
by clicking on the + sign. The items in this listing can be used to populate the Modbus items
list on the right side of the tab by dragging and dropping them into the Modbus list.
5.3.2.2 The Enron Modbus Protocol
An
Enron Modbus
list contains 4 nodes on the Modbus tree, Coils , Short Integers, Long
Integers, and Floating Point (Figure 5-11). Coils are Boolean data points which have a
value of either 0 or 1. To that end, data points entered into the Coils node would usually be
data points that are simple status indicators, indicating the status of a given alarm, input, or
output. If the value of the data point is 0, the status of the logged alarm, relay, etc, would be
off, and if the value is 1, the status would be on. Short integers are 16 bit whole numbers with
either positive or negative sign. Long integers are 32 bit whole numbers with either positive or
negative sign. Floating point values are also 32 bit numbers, but unlike the integers they do
not have a sign, but they do have decimal points.
5.3.2.3 The Modicon 16 Protocol
A
Modicon 16 Modbus
list contains 4 nodes on the Modbus tree. They are Output Status,
Input Status, Input Register, and Output Register . The Input and Output Status nodes
contain Boolean data points. Data points in the Input Status node are able to be written to.
Data points in the Output Status node are read-only, so this node would contain data points
such as alarm, input, and output status that cannot be changed remotely.
Output Registers are data points that are read-only outputs of analyzer data, such as
calculated concentration. Please note that Modicon 16 only outputs data as 16 bit numbers,
so the display of decimal points in this type of Modbus list is not possible.
Input Registers contains non-Boolean data points that can be written to.
5.3.2.4 Modicon with Floating Point Protocol
The Modicon with Floating Point (MODICON 32) list contains 4 main nodes on the Modbus
tree. However, the Input and Output Registers contain sub-nodes. They are Register Short,
Register Long , and Register Float . Thus, the input and output registers can output data in
16-bit, 32-bit, or 32-bit with floating point in the Modicon with Floating Point Modbus list.