Revision 14
121 August 02, 2019
5.16.2 Modicon 16
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 Output Status node are able to be written to,
so the Output Status node can contain data points such as stream requests. If the value in a
given stream was changed from 0 to 1, the analyzer would then initiate that stream. Data
points in the Input Status node are read-only, so this node would contain data points such as
alarm, input, and output status that cannot be changed remotely. Input 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. Output Register contains non-Boolean data points
that can be written to remotely. These would include such things as tape length, calibration
gas concentration, and gain factor.
5.16.3 Modicon with Floating Point
Just like the Modicon 16 Modbus list, 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.
5.16.4 A Typical Modbus Setup
The default Modbus setup for the analyzer uses the Modicon with Floating point format. Data
points are added to the Modbus list in much the same way that data points are added to the
Archive. Figure 5-36 shows a typically configured Modicon with Floating Point Modbus list.
On the left hand side of the screen is a narrow field entitled Available Points. Under this field
are seven expandable nodes which are: Streams 1 through 4, Inputs/Outputs, Alarms/Status
and Actions. Figure 5-36 shows a typical Modcon list with Floating Point List and Figure 5-37
shows all the available points under each expandable node.
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