Galvanic Applied Sciences AccuChrome MA2963, Operation Manual

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Revision 4 90 12/15/2018
8.2 The Modbus List Page
The Modbus List page (Figure 8-1) lists general information about the Modbus data protocol.
The format will depend, in part on the selections made on the lop line of the page.
Type
- There are three Modbus types: Enron (Section 8.2.1), Modicon 16 (Section 8.2.2) and
Modicon with Floating Point (Section 8.2.3).
Address
- Indicates the Modbus address of the analyzer.
Endian - allows for selection of Big Endian or Little Endian. This parameter defines if the
most significant bit or the least significant bit for a word is transmitted first.
32-Bit Register Swap
- For 32 bit registers that are transmitted as 2 16 bit words, this
parameter determines if the integer or the fraction part of the number is transmitted first in the
first word.
Slave/Master
- If Slave is selected, the Modbus list will act as a slave and will transmit data
only when it has been interrogated. If Master is selected, then the Modbus list will transmit
data at the end of each cycle to a slave device.
8.2.1 Modbus List Page - Enron Mode
An Enron Modbus list contains 4 nodes on the Modbus tree. They are Coils, Short Integers,
Long Integers,
and
Floating Point
. Coils are Boolean data points - that is to say, they 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. Typically, they refer to
concentration information.
The left column on the Modbus List page indicates the available points and the right column
lists the items, the
Register
where the data is transmitted and the
Real Time Value
. If desired
the user can indicate a Manual Set Value by clicking on the
Enable Manual Set Value
box
and then entering the value in the adjacent field, then pressing the
Write to Analyzer
icon. As
an example, the user might want to adjust the Hour field for the onset of daylight saving time .
A typical example of Short integers is presented in Figure 8-2 and an example of Floating
Points is presented in Figure 8-3.