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PM Integrated Controller • 50 • Chapter 4 Home Page

Modbus Introduction to the Modbus Protocol (cont.)

All Modbus registers are 16-bits and as displayed in this User's Guide are relative addresses (actual).

Some legacy software packages limit available Modbus registers to 40000 to 49999 (5 digits). Many applica-

tions today require access to all available Modbus registers which range from 400000 to 465535 (6 digits). For

parameters listed as float, notice that only one (low order) of the two registers is listed; this is true through-

out this document. By default, the low order word contains the two low bytes of the 32-bit parameter. As an

example, look in the Operations Page for the Analog Input Value. Find the column identified in the header

as Modbus and notice that it lists register 360. Because this parameter is a float it is actually represented by

registers 360 (low order bytes) and 361 (high order bytes). The Modbus specification does not dictate which

Page, [Com ] Menu) from the default low/high [lohi] to high/low [hilo].

Note:

With the release of firmware revision 7.00 and above new functions where introduced into this product line.

With the introduction of these new functions there was a reorganization of Modbus registers. Notice in the

column identified as Modbus the reference to Map 1 and Map 2 registers for each of the various parameters.

If the new functions, namely; Math, Linearization, Process Value, Real Time Clock and the Special Output

Function are to be used than use Map 2 Modbus registers. If the new functions of this product line are not

to be used, Map 1 (legacy PM controls) Modbus registers will be sufficient. The Modbus register mapping

[map] can be changed in the Setup Page under the [Com] Menu. This setting will apply across the con-

trol.

It should also be noted that some of the cells in the Modbus column contain wording pertaining to an off-

set. Several parameters in the control contain more than one instance; such as, profiles (4), alarms (4), analog

inputs (2), etc... The Modbus register shown always represents instance one. Take for an example the Alarm

Silence parameter found in the Setup Page under the Alarm Menu. Instance one of Map 1 is shown as ad-

dress 1490 and +50 is identified as the offset to the next instance. If there was a desire to read or write to

instance 3 simply add 100 to 1490 to find its address, in this case, the instance 3 address for Alarm Silence is

1590.

The Modbus communications instance can be either 1 or 2 depending on the part number.

Instance 1:

PM _ _ _ _ _ - [1] _ _ _ _ _ _

Instance 2:

PM _ _ _ _ _ - [2] _ _ _ _ _ _

To learn more about the Modbus protocol point your browser to http://www.modbus.org.

Common Industrial Protocol (CIP) Introduction to CIP

Both DeviceNet and EtherNet/IP use open object based programming tools and use the same addressing

scheme. In the following menu pages notice the column header identified as CIP. There you will find the

Class, Instance and Attribute in hexadecimal, (decimal in parenthesis) which makes up the addressing for

both protocols.

The CIP communications instance will always be instance 2.

Data Types Used with CIP

int = Signed 16-bit integer

uint = Signed 16-bit integer

dint = Signed 32-bits, long

real = Float, IEEE 754 32-bit

string = ASCII, 8 bits per character

sint = Signed 8 bits , byte

To learn more about the DeviceNet and EtherNet/IP protocol point your browser to http://www.odva.org.